PDIA6 and Maspin in Prostate Cancer

BACKGROUND/AIM

PDIA6 is a disulphide isomerase of the PDI family, known to mediate disulphide bond formation in the endoplasmic reticulum. However, PDI-related proteins also function in other parts of the cell and PDIA6 has been shown to be involved in many types of cancers. We previously identified PDIA6 as a putative Maspin interactor. Maspin has itself been implicated in prostate cancer progression. Our aim was to further explore the roles of Maspin in prostate cancer and establish whether PDIA6 is also involved in prostate cancer.

MATERIALS AND METHODS

RNA levels of PDIA6 and Maspin in prostate cell lines were measured using RT-PCR. Bioinformatics analysis of the TCGA database was used to find RNA levels of PDIA6 and Maspin in prostate cancer. siRNAs were used to knock-down PDIA6, and proliferation and migration assays were conducted on those cells.

RESULTS

PDIA6 and Maspin RNA were shown to be expressed at varying levels in prostate cell lines. RNAseq data showed that PDIA6 expression was significantly increased in prostate adenocarcinoma samples, while Maspin RNA expression was decreased. When PDIA6 expression was knocked-down using siRNA in prostate cell lines, proliferation was decreased substantially in the two prostate cancer cell lines (DU145 and PC3) and also decreased in the normal prostate cell line (PNT1a), though less strongly.

CONCLUSION

PDIA6 expression is higher in prostate cancer cells compared to normal prostate cells. Decreasing PDIA6 expression decreases proliferation. Thus, PDIA6 is a promising target for prostate cancer therapeutics.

Synthetic biology for improved hydrogen production in Chlamydomonas reinhardtii

Hydrogen is a clean alternative to fossil fuels. It has applications for electricity generation and transportation and is used for the manufacturing of ammonia and steel. However, today, H₂ is almost exclusively produced from coal and natural gas. As such, methods to produce H₂ that do not use fossil fuels need to be developed and adopted. The biological manufacturing of H₂ may be one promising solution as this process is clean and renewable. Hydrogen is produced biologically via enzymes called hydrogenases. There are three classes of hydrogenases namely [FeFe], [NiFe] and [Fe] hydrogenases. The [FeFe] hydrogenase HydA1 from the model unicellular algae Chlamydomonas reinhardtii has been studied extensively and belongs to the A1 subclass of [FeFe] hydrogenases that have the highest turnover frequencies amongst hydrogenases (21,000 ± 12,000 H₂ s⁻¹ for CaHydA from Clostridium acetobutyliticum). Yet to date, limitations in C. reinhardtii H₂ production pathways have hampered commercial scale implementation, in part due to O₂ sensitivity of hydrogenases and competing metabolic pathways, resulting in low H₂ production efficiency. Here, we describe key processes in the biogenesis of HydA1 and H₂ production pathways in C. reinhardtii. We also summarize recent advancements of algal H₂ production using synthetic biology and describe valuable tools such as high‐throughput screening (HTS) assays to accelerate the process of engineering algae for commercial biological H₂ production.

Cardiac Surgery in Patients With Blood Disorders

Blood disorders that can contribute to abnormal bleeding can have a detrimental effect during cardiac surgery. Patients who are known to have such pathologies should be investigated thoroughly and cautious measures would need to be taken when cardiac surgery is needed in this cohort. The majority of current literature for cardiac surgery in patients with von Willebrand Disease and haemophilia are case reports. Nevertheless, evidence shows that optimising factor levels pre, intra and postoperatively offers outcomes similar to that of patients without these disorders. Preoperative screening followed by appropriate iron therapy reduces mortality for patients with anaemia. In this group, haemoglobin levels can be improved postoperatively through iron supplementation. The management strategy of cardiac surgery for people with blood disorders requires a multidisciplinary approach that is highly individualised for each patient. It is essential to adequately adjust preoperative, perioperative and postoperative care to the patient's blood disorder in order to achieve outcomes similar to that of patients without blood disorders.

TOAC spin-labeled peptides tailored for DNP-NMR studies in lipid membrane environments

The benefit of combining in-cell solid-state dynamic nuclear polarization (DNP) NMR and cryogenic temperatures is providing sufficient signal/noise and preservation of bacterial integrity via cryoprotection to enable in situ biophysical studies of antimicrobial peptides. The radical source required for DNP was delivered into cells by adding a nitroxide-tagged peptide based on the antimicrobial peptide maculatin 1.1 (Mac1). In this study, the structure, localization, and signal enhancement properties of a single (T-MacW) and double (T-T-MacW) TOAC (2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxylic acid) spin-labeled Mac1 analogs were determined within micelles or lipid vesicles. The solution NMR and circular dichroism results showed that the spin-labeled peptides adopted helical structures in contact with micelles. The peptides behaved as an isolated radical source in the presence of multilamellar vesicles, and the electron paramagnetic resonance (EPR) electron-electron distance for the doubly spin-labeled peptide was ∼1 nm. The strongest paramagnetic relaxation enhancement (PRE) was observed for the lipid NMR signals near the glycerol-carbonyl backbone and was stronger for the doubly spin-labeled peptide. Molecular dynamics simulation of the T-T-MacW radical source in phospholipid bilayers supported the EPR and PRE observations while providing further structural insights. Overall, the T-T-MacW peptide achieved better ¹³C and ¹⁵N signal NMR enhancements and ¹H spin-lattice T₁ relaxation than T-MacW.

Evaluation of spot patterns and carapace abnormalities of an Endangered freshwater turtle, Clemmys guttata, as a potential tool for population assignment

Many of the world’s contemporary species of turtle are extinct or threatened with extinction due to habitat loss, increases in anthropogenic sources of mortality, and poaching (illegal collection). The slow life-history strategy of most turtle species magnifies the effects of poaching because the loss of even a few mature individuals can impact population growth. Returning poached turtles to their population of origin, where possible, can mitigate these effects, but identifying the origin of these individuals can be challenging. We hypothesized that spot patterns might allow assignment of Endangered spotted turtles Clemmys guttata to their population of origin. We characterized and compared spot patterns from carapace photographs of 126 individuals from 10 sites. To explore other types of information these photographs might provide, we also documented carapacial scute abnormalities and quantified their association with genetic diversity and latitude. Spot pattern similarity was not higher within populations than among populations and did not accurately differentiate populations. Carapacial scute abnormalities occurred in 82% of turtles and were not correlated with estimates of neutral genetic diversity. Abnormalities were positively correlated with latitude, implicating thermal stress during the early stages of development in the generation of some scute deformities. However, this relationship became non-significant when line (scute seam) abnormalities were excluded from the data, suggesting a different primary cause for the more severe scute deformities. Further research should continue to investigate the drivers of these deformities, as monitoring shifts in the frequency of scute deformities may provide relevant information for conservation and recovery of endangered turtles.

Outcomes of cardiac surgery in Jehovah's Witness patients: A review

Objective:

To review current literature evidence on outcomes of cardiac surgery in Jehovah’s Witness patients.

Methods:

A comprehensive electronic literature search was done from 2010 to 20th August 2020 identifying articles that discussed optimisation/outcomes of cardiac surgery in Jehovah’s Witness either as a solo cohort or as comparative to non-Jehovah’s Witnesses. No limit was placed on place of publication and the evidence has been summarised in a narrative manner within the manuscript.

Results:

The outcomes of cardiac surgery in Jehovah’s Witness patients has been described, and also compared, to non-Witness patients within a number of case reports, case series and comparative cohort studies. Many of these studies note no significant differences between outcomes of the two groups for a number of variables, including mortality. Pre-, intra and post-operative optimisation of the patients by a multidisciplinary team is important to achieve good outcomes.

Conclusion:

The use of a bloodless protocol for Jehovah’s Witnesses does not appear to significantly impact upon clinical outcomes when compared to non-Witness patients, and it has even been suggested that a bloodless approach could provide advantages to all patients undergoing cardiac surgery. Larger cohorts and research across multiple centres into the long term outcomes of these patients is required.

Phosphorylation of Troponin I finely controls the positioning of Troponin for the optimal regulation of cardiac muscle contraction

Troponin is the Ca²⁺ molecular switch that regulates striated muscle contraction. In the heart, troponin Ca²⁺ sensitivity is also modulated by the PKA-dependent phosphorylation of a unique 31-residue N-terminal extension region of the Troponin I subunit (NH₂-TnI). However, the detailed mechanism for the propagation of the phosphorylation signal through Tn, which results in the enhancement of the myocardial relaxation rate, is difficult to examine within whole Tn. Several models exist for how phosphorylation modulates the troponin response in cardiac cells but these are mostly built from peptide-NMR studies and molecular dynamics simulations. Here we used a paramagnetic spin labeling approach to position and track the movement of the NH₂-TnI region within whole Tn. Through paramagnetic relaxation enhancement (PRE)-NMR experiments, we show that the NH₂-TnI region interacts with a broad surface area on the N-domain of the Troponin C subunit. This region includes the Ca²⁺ regulatory Site II and the TnI switch-binding site. Phosphorylation of the NH₂-TnI both weakens and shifts this region to an adjacent site on TnC. Interspin EPR distances between NH₂-TnI and TnC further reveal a phosphorylation induced re-orientation of the TnC N-domain under saturating Ca²⁺ conditions. We propose an allosteric model where phosphorylation triggered cooperative changes in both the interaction of the NH₂-TnI region with TnC, and the re-orientation of the TnC interdomain orientation, together promote the release of the TnI switch-peptide. Enhancement of the myocardial relaxation rate then occurs. Knowledge of this unique role of phosphorylation in whole Tn is important for understanding pathological processes affecting the heart.

Outcomes in minimally invasive double valve surgery

OBJECTIVE

To review current literature evidence on outcomes of minimally invasive double valve surgeries (MIS).

METHODS

A comprehensive electronic literature search was done from inception to 20th June 2020 identifying articles that discussed outcomes of minimally invasive approach in double valve surgeries either as a solo cohort or as comparative to conventional sternotomies. No limit was placed on time and place of publication and the evidence has been summarized in narrative manner within the manuscript.

RESULTS

Majority of current literature reported similar perioperative and clinical outcomes between MIS and conventional median sternotomy; except that MIS has better cosmetic effects and pain control. Nevertheless, minimal invasive techniques are associated with longer cardiopulmonary bypass and aortic cross-clamp times which may have impact on the reported outcomes and overall morbidity and mortality rates.

CONCLUSION

Minimally invasive double valve surgery continues to develop, but scarcity in the literature suggests uptake is slow, possibly due to the learning curve associated with MIS. Many outcomes appear to be comparable to conventional sternotomy. There is need for larger, multi-center, and randomized trial to fully evaluate and establish the early, mid- and long-term morbidity and mortality rates associated with both techniques.

The role of socio-economic status and energy-density in Australian women of child-bearing age

INTRODUCTION

An optimal diet is imperative in preparing women for pregnancy and this may be influenced by socio-economic status (SES). This research aims to investigate the role of SES on the dietary energy density (ED) in Australian women of preconception age.

METHODS

A secondary analysis of the Australian National Nutrition and Physical Activity Survey 2011-12 for females aged 18-39 years (n = 1617) was conducted. Dietary intake was assessed by 24-hr recalls and dietary ED by dietary energy per weight (kJ.g^-1 ). ED was further categorised as ED of foods and beverages separately. SES was assessed by three variables: Socio-Economic Indexes for Areas (SEIFA), developed by the Australian Bureau of Statistics; income decile; and level of education. Linear mixed model regressions were used to identify associations between ED and SES.

RESULTS

The median ED for food, beverages and combined food and beverages was 9.38 kJ g^-1 , 1.02 kJ g^-1 and 7.11 kJ g^-1 , respectively. No significant variation was explained by SES variables when analysing combined ED in the adjusted model or ED from foods. Income decile reduced ED of beverages, although with little effect (coefficient: -0.04, P = 0.002). Significant confounders included inactivity, which increased ED in both combined ED and ED foods (coefficient: 0.51, P = 0.001 and coefficient: 0.78, P < 0.001).

CONCLUSIONS

SES explained little variation in dietary ED in women of childbearing age. A large proportion of women had high energy-dense diets regardless of their SES. These findings suggest that a large proportion of women, who may become pregnant, have diets that exceed the international recommendations for dietary energy density.

Characterization of optofluidic devices for the sorting of sub-micrometer particles

In this work, we investigate methods of fabricating a device for the optical actuation of nanoparticles. To create the microfluidic channel, we pursued three fabrication methods: SU-8 to molded polydimethylsiloxane soft lithography, laser etching of glass, and deep reactive ion etching of fused silica. We measured the surface roughness of the etched sidewalls, and the laser power transmission through each device. We then measured the radiation pressure on 0.5-µm particles in the best-performing fabricated device (etched fused silica) and in a square glass capillary.

Constructing a structural model of troponin using site-directed spin labeling: EPR and PRE-NMR

The relative ease of introducing a paramagnetic species onto a protein, and advances in electron paramagnetic resonance (EPR) over the past two decades, have established spin labeling as a vital structural biology technique for revealing the functional workings of the troponin muscle regulatory complex-an ~80 kDa heterotrimeric protein switch for turning on striated muscle contraction. Through the site-directed spin labeling (SDSL) of cysteine residues at key sites in troponin, a molecular-level understanding of the troponin muscle regulatory system across all levels of structural hierarchy has been achieved. Through the application of EPR, mobility and accessibility trends in the EPR signals of the spin labels attached to consecutive residues can reveal the secondary structure of troponin elements and also help map the interaction between subunits. Distance restraints calculated from the interspin interactions between spin label pairs have helped with building a structural model of the troponin complex. Further, when SDSL is paired with NMR, paramagnetic relaxation enhancement (PRE)-NMR has been used to obtain high-resolution structural detail for both intra- and interdomain interactions in troponin and revealed details of protein conformational changes and dynamics accompanying troponin function. In this review, we provide an overview of the SDSL labeling methodology and its application towards building a dynamic structural model of the multi-subunit troponin complex which details the calcium-induced conformational changes intimately linked to muscle regulation. We also describe how the SDSL method, in conjunction with EPR or NMR, can be used to obtain insights into structural perturbations to troponin caused by disease-causing mutations.

A conserved GXXXG motif in the transmembrane domain of CLIC proteins is essential for their cholesterol-dependant membrane interaction

BACKGROUND

Sterols have been reported to modulate conformation and hence the function of several membrane proteins. One such group is the Chloride Intracellular Ion Channel (CLIC) family of proteins. The CLIC protein family consists of six evolutionarily conserved protein members in vertebrates. These proteins exist as both monomeric soluble proteins and as membrane bound proteins. To date, the structure of their membrane-bound form remains unknown. In addition to several studies indicating cellular redox environment and pH as facilitators of CLIC1 insertion into membranes, we have also demonstrated that the spontaneous membrane insertion of CLIC1 is regulated by membrane cholesterol.

METHOD

We have performed Langmuir-film, Impedance Spectroscopy and Molecular Docking Simulations to study the role of this GXXXG motif in CLIC1 interaction with cholesterol.

RESULTS

Unlike CLIC1-wild-type protein, the G18A and G22A mutants, that form part of the GXXXG motif, showed much slower initial kinetics and lower ion channel activity compared to the native protein. This difference can be attributed to the significantly reduced membrane interaction and insertion rate of the mutant proteins and/or slower formation of the final membrane configuration of the mutant proteins once in the membrane.

CONCLUSION

In this study, our findings uncover the identification of a GXXXG motif in CLIC1, which likely serves as the cholesterol-binding domain, that facilitates the protein's membrane interaction and insertion. Furthermore, we were able to postulate a model by which CLIC1 can autonomously insert into membranes to form functional ion channels.

GENERAL SIGNIFICANCE

Members of the CLIC family of proteins demonstrate unusual structural and dual functional properties - as ion channels and enzymes. Elucidating how the CLIC proteins' interact with membranes, thus allowing them to switch between their soluble and membrane form, will provide key information as to a mechanism of moonlighting activity and a novel regulatory role for cholesterol in such a process.

Nuclear singlet relaxation by scalar relaxation of the second kind in the slow-fluctuation regime

The singlet state of nuclear spin-1/2 pairs is protected against many common relaxation mechanisms. Singlet order, which is defined as the population difference between the nuclear singlet and triplet states, usually decays more slowly than the nuclear magnetization. Nevertheless, some decay mechanisms for nuclear singlet order persist. One such mechanism is called scalar relaxation of the second kind (SR2K) and involves the relaxation of additional nuclei ("third spins") which have scalar couplings to the spin-1/2 pair. This mechanism requires a difference between the couplings of at least one third spin with the two members of the spin-1/2 pair, and depends on the longitudinal relaxation time of the third spin. The SR2K mechanism of nuclear singlet relaxation has previously been examined in the case where the relaxation rate of the additional spins is on the time scale of the nuclear Larmor frequency. In this paper, we consider a different regime, in which the longitudinal relaxation of the third spins is on a similar time scale to the J-coupling between the members of the spin pair. This regime is often encountered when the spin-1/2 pair has scalar couplings to nearby deuterium nuclei. We show that the SR2K mechanism may be suppressed in this regime by applying a radiofrequency field which is resonant either with the members of the spin pair, or with the third spins. These phenomena are analyzed theoretically and by numerical simulations, and demonstrated experimentally on a diester of [¹³C₂, ²H₂]-labeled fumarate in solution.

Characterization of the L29Q Hypertrophic Cardiomyopathy Mutation in Cardiac Troponin C by Paramagnetic Relaxation Enhancement Nuclear Magnetic Resonance

The key events in regulating muscle contraction involve the troponin (Tn) heterotrimeric protein complex in which the binding to and release of Ca²⁺ from the highly conserved troponin C (TnC) subunit trigger a series of structural changes within Tn, and the other thin filament proteins, to result in contraction. In the heart, the control of contraction and relaxation events can be altered by many single-point mutations that may result in cardiomyopathy and sometimes sudden cardiac death. Here we have examined the structural effects of one hypertrophic cardiomyopathy mutation, L29Q, on Ca²⁺-induced structural transitions within whole TnC. This mutation is of particular interest as several physiological and structural studies have indicated that the response of TnC to Ca²⁺ binding is altered in the presence of the L29Q mutation, but the structural nature of these changes continues to be debated. In addition, little is known about the effect of this mutation in the Ca²⁺ free state. Here we have used paramagnetic relaxation enhancement nuclear magnetic resonance (PRE-NMR) to assess the structural effects arising from the L29Q mutation. PRE-NMR distances obtained from a nitroxide spin-label at Cys84 showed that the L29Q mutation perturbs the structure of the TnC N-domain in the presence and absence of Ca²⁺, with a more "open" TnC N-domain observed in the apo form. In addition, binding of Ca²⁺ to the TnC-L29Q construct triggers a change in the orientation between the two domains of TnC. Together, these structural perturbations, revealed by PRE-NMR, provide insight into the pathogenesis of this mutation.

Influence of surface chemistry on the formation of a protein corona on nanodiamonds

The protein corona of nanodiamonds is dominated by low molecular weight proteins and is largely independent of surface chemistry. The pre-incubation of nanodiamonds in serum and the formation of a protein corona decrease the production of reactive oxygen species, increasing the cell viability of macrophages.

Using behavioural insights to increase HIV self-sampling kit returns: a randomized controlled text message trial to improve England's HIV self-sampling service

OBJECTIVES

The aim of the study was to determine whether behaviourally informed short message service (SMS) primer and reminder messages could increase the return rate of HIV self-sampling kits ordered online.

METHODS

The study was a 2 × 2 factorial design randomized control trial. A total of 9585 individuals who ordered a self-sampling kit from www.freetesting.hiv different SMS combinations: 1) standard reminders sent days 3 and 7 after dispatch (control); 2) primer sent 1 day after dispatch plus standard reminders; 3) behavioural insights (BI) reminders (no primer); or 4) primer plus BI reminders. The analysis was restricted to individuals who received all messages (n = 8999). We used logistic regression to investigate independent effects of the primer and BI reminders and their interaction. We explored the impact of sociodemographic characteristics on kit return as a secondary analysis.

RESULTS

Those who received the primer and BI reminders had a return rate 4% higher than that of those who received the standard messages. We found strong evidence of a positive effect of the BI reminders (odds ratio 1.13; 95% confidence interval 1.04-1.23; P = 0.003) but no evidence for an effect of the primer, or for an interaction between the two interventions. Odds of kit return increased with age, with those aged ≥ 65 years being almost 2.5 times more likely to return the kit than those aged 25-34 years. Men who have sex with men were 1.5-4.5 times more likely to return the kit compared with other sexual behaviour and gender identity groups. Non-African black clients were 25% less likely to return the kit compared with other ethnicities.

CONCLUSIONS

Adding BI to reminder messages was successful in improving return rates at no additional cost.

Judicious use of prophylactic antimicrobials to reduce abdominal surgical site infections in periparturient cows: part 1 - a risk factor review

Surgical site infections (SSI) are an uncommon, but significant, consequence of surgical interventions. There are very few studies investigating SSI risk in veterinary medicine, and even fewer in cattle, despite the fact that major surgeries are commonly conducted on livestock. Furthermore, the suboptimal conditions under which such surgeries are frequently performed on livestock could be considered an important risk factor for the development of SSIs. With increasing public concern over the contribution of veterinary-prescribed antimicrobials to the emergence of antimicrobial-resistant bacteria in people, there is widespread scrutiny and criticism of antimicrobial use in livestock production medicine systems. While the causal link between antimicrobial resistance in livestock and people is heavily debated, it is clear that the prevalence of antimicrobial resistance, in any population, is closely correlated with the antimicrobial 'consumption' within that population. As the veterinary profession explores ways of addressing the emergence and selection of antimicrobial-resistant bacteria in food-producing animals, there is a need for veterinarians and producers to carefully consider all areas of antimicrobial use, and employ an evidence-based approach in designing appropriate clinical protocols. This paper aims to review current knowledge regarding the risk factors related to abdominal SSI in periparturient cows, and to encourage practitioners to judiciously evaluate both their standard operating procedures and their use of antimicrobials in these situations. In a second paper, to be published in a subsequent issue of Veterinary Record, these principles will be used to provide specific evidence-based recommendations for antimicrobial use in bovine abdominal surgery.

Interaction of Human Chloride Intracellular Channel Protein 1 (CLIC1) with Lipid Bilayers: A Fluorescence Study

Chloride intracellular channel protein 1 (CLIC1) is very unusual as it adopts a soluble glutathione S-transferase-like canonical fold but can also autoinsert into lipid bilayers to form an ion channel. The conversion between these forms involves a large, but reversible, structural rearrangement of the CLIC1 module. The only identified environmental triggers controlling the metamorphic transition of CLIC1 are pH and oxidation. Until now, there have been no high-resolution structural data available for the CLIC1 integral membrane state, and consequently, a limited understanding of how CLIC1 unfolds and refolds across the bilayer to form a membrane protein with ion channel activity exists. Here we show that fluorescence spectroscopy can be used to establish the interaction and position of CLIC1 in a lipid bilayer. Our method employs a fluorescence energy transfer (FRET) approach between CLIC1 and a dansyl-labeled lipid analogue to probe the CLIC1-lipid interface. Under oxidizing conditions, a strong FRET signal between the single tryptophan residue of CLIC1 (Trp35) and the dansyl-lipid analogue was detected. When considering the proportion of CLIC1 interacting with the lipid bilayer, as estimated by fluorescence quenching experiments, the FRET distance between Trp35 and the dansyl moiety on the membrane surface was determined to be ∼15 Å. This FRET-detected interaction provides direct structural evidence that CLIC1 associates with membranes. The results presented support the current model of an oxidation-driven interaction of CLIC1 with lipid bilayers and also propose a membrane anchoring role for Trp35.

CLIC1 regulates dendritic cell antigen processing and presentation by modulating phagosome acidification and proteolysis

Intracellular chloride channel protein 1 (CLIC1) participates in inflammatory processes by regulating macrophage phagosomal functions such as pH and proteolysis. Here, we sought to determine if CLIC1 can regulate adaptive immunity by actions on dendritic cells (DCs), the key professional antigen presenting cells. To do this, we first generated bone marrow-derived DCs (BMDCs) from germline CLIC1 gene-deleted (CLIC1^−/−) and wild-type (CLIC1^+/+) mice, then studied them in vitro and in vivo. We found phagocytosis triggered cytoplasmic CLIC1 translocation to the phagosomal membrane where it regulated phagosomal pH and proteolysis. Phagosomes from CLIC1^−/− BMDCs displayed impaired acidification and proteolysis, which could be reproduced if CLIC1^+/+, but not CLIC1^−/− cells, were treated with IAA94, a CLIC family ion channel blocker. CLIC1^−/− BMDC displayed reduced in vitro antigen processing and presentation of full-length myelin oligodendrocyte glycoprotein (MOG) and reduced MOG-induced experimental autoimmune encephalomyelitis. These data suggest that CLIC1 regulates DC phagosomal pH to ensure optimal processing of antigen for presentation to antigen-specific T-cells. Further, they indicate that CLIC1 is a novel therapeutic target to help reduce the adaptive immune response in autoimmune diseases.

Summary: DC phagosomes from CLIC1^−/− mice display impaired acidification and in vivo and in vitro antigen processing and presentation, revealing CLIC1^−/− as a potential therapeutic target in reducing the adaptive immune response in autoimmune diseases.

Nano-assembly of nanodiamonds by conjugation to actin filaments

Fluorescent nanodiamonds (NDs) are remarkable objects. They possess unique mechanical and optical properties combined with high surface areas and controllable surface reactivity. They are non-toxic and hence suited for use in biological environments. NDs are also readily available and commercially inexpensive. Here, the exceptional capability of controlling and tailoring their surface chemistry is demonstrated. Small, bright diamond nanocrystals (size ˜30 nm) are conjugated to protein filaments of actin (length ˜3-7 µm). The conjugation to actin filaments is extremely selective and highly target-specific. These unique features, together with the relative simplicity of the conjugation-targeting method, make functionalised nanodiamonds a powerful and versatile platform in biomedicine and quantum nanotechnologies. Applications ranging from using NDs as superior biological markers to, potentially, developing novel bottom-up approaches for the fabrication of hybrid quantum devices that would bridge across the bio/solid-state interface are presented and discussed.

Members of the chloride intracellular ion channel protein family demonstrate glutaredoxin-like enzymatic activity

The Chloride Intracellular Ion Channel (CLIC) family consists of six evolutionarily conserved proteins in humans. Members of this family are unusual, existing as both monomeric soluble proteins and as integral membrane proteins where they function as chloride selective ion channels, however no function has previously been assigned to their soluble form. Structural studies have shown that in the soluble form, CLIC proteins adopt a glutathione S-transferase (GST) fold, however, they have an active site with a conserved glutaredoxin monothiol motif, similar to the omega class GSTs. We demonstrate that CLIC proteins have glutaredoxin-like glutathione-dependent oxidoreductase enzymatic activity. CLICs 1, 2 and 4 demonstrate typical glutaredoxin-like activity using 2-hydroxyethyl disulfide as a substrate. Mutagenesis experiments identify cysteine 24 as the catalytic cysteine residue in CLIC1, which is consistent with its structure. CLIC1 was shown to reduce sodium selenite and dehydroascorbate in a glutathione-dependent manner. Previous electrophysiological studies have shown that the drugs IAA-94 and A9C specifically block CLIC channel activity. These same compounds inhibit CLIC1 oxidoreductase activity. This work for the first time assigns a functional activity to the soluble form of the CLIC proteins. Our results demonstrate that the soluble form of the CLIC proteins has an enzymatic activity that is distinct from the channel activity of their integral membrane form. This CLIC enzymatic activity may be important for protecting the intracellular environment against oxidation. It is also likely that this enzymatic activity regulates the CLIC ion channel function.

Ca2+-induced PRE-NMR changes in the troponin complex reveal the possessive nature of the cardiac isoform for its regulatory switch

The interaction between myosin and actin in cardiac muscle, modulated by the calcium (Ca²⁺) sensor Troponin complex (Tn), is a complex process which is yet to be fully resolved at the molecular level. Our understanding of how the binding of Ca²⁺ triggers conformational changes within Tn that are subsequently propagated through the contractile apparatus to initiate muscle activation is hampered by a lack of an atomic structure for the Ca²⁺-free state of the cardiac isoform. We have used paramagnetic relaxation enhancement (PRE)-NMR to obtain a description of the Ca²⁺-free state of cardiac Tn by describing the movement of key regions of the troponin I (cTnI) subunit upon the release of Ca²⁺ from Troponin C (cTnC). Site-directed spin-labeling was used to position paramagnetic spin labels in cTnI and the changes in the interaction between cTnI and cTnC subunits were then mapped by PRE-NMR. The functionally important regions of cTnI targeted in this study included the cTnC-binding N-region (cTnI57), the inhibitory region (cTnI143), and two sites on the regulatory switch region (cTnI151 and cTnI159). Comparison of ¹H-¹⁵N-TROSY spectra of Ca²⁺-bound and free states for the spin labeled cTnC-cTnI binary constructs demonstrated the release and modest movement of the cTnI switch region (∼10 Å) away from the hydrophobic N-lobe of troponin C (cTnC) upon the removal of Ca²⁺. Our data supports a model where the non-bound regulatory switch region of cTnI is highly flexible in the absence of Ca²⁺ but remains in close vicinity to cTnC. We speculate that the close proximity of TnI to TnC in the cardiac complex is favourable for increasing the frequency of collisions between the N-lobe of cTnC and the regulatory switch region, counterbalancing the reduction in collision probability that results from the incomplete opening of the N-lobe of TnC that is unique to the cardiac isoform.

Diet quality of Australian breast cancer survivors: a cross-sectional analysis from the Australian Longitudinal Study on Women's Health

BACKGROUND

Evidence supports strong associations between healthful eating patterns and maintaining a healthy weight with favourable health outcomes for breast cancer survivors (BCS). The present study aimed to evaluate the diet quality of Australian BCS and to determine whether diet quality differed between BCS and age-matched healthy controls (HC) or by geographical location.

METHODS

This cross-sectional study included 281 BCS and 4069 HC from the Australian Longitudinal Study on Women's Health mid-aged cohort completing Survey 3 in 2001. Data from the Dietary Questionnaire for Epidemiological Studies food frequency questionnaire were used to calculate the Australian Recommended Food Score (ARFS), a validated summary estimate of diet quality based on adherence to the Australian dietary guidelines.

RESULTS

The mean (SD) ARFS of the BCS group was 33.2 (9.4) out of a maximum of 74. Mean (SD) total ARFS and component scores of BCS did not differ from the HC group [32.9 (8.7)] and no differences were found in ARFS between urban and rural BCS.

CONCLUSIONS

This is the first study dedicated exclusively to describing the diet quality of Australian BCS. Although no difference was found when comparisons were made with a HC group, there is considerable room for improvement in the diet quality of Australian BCS. Given research suggesting higher risk of chronic conditions such as obesity amongst BCS, and the recognition of optimising diet quality as a key factor in health promotion for all population groups, data from the present study suggest the need for research targeting the feasibility and impact of improving diet quality of Australian BCS.

Oral vaccination and protection of red foxes (Vulpes vulpes) against rabies using ONRAB, an adenovirus-rabies recombinant vaccine

Twenty-seven red foxes (Vulpes vulpes) were each offered a bait containing ONRAB, a recombinant oral rabies vaccine that uses a human adenovirus vector to express the immunogenic rabies virus glycoprotein; 10 controls received no vaccine baits. Serum samples collected from all foxes before treatment, and each week post-treatment for 16 weeks, were tested for the presence of rabies virus neutralizing antibody (RVNA). In the bait group, a fox was considered a responder to vaccination if serum samples from 3 or more consecutive weeks had RVNA ≥0.5 IU/ml. Using this criterion, 79% of adult foxes (11/14) and 46% of juveniles (6/13) responded to vaccination with ONRAB. Serum RVNA of adults first tested positive (≥0.5 IU/ml) between weeks 1 and 3, about 4 weeks earlier than in juveniles. Adults also responded with higher levels of RVNA and these levels were maintained longer. Serum samples from juveniles tested positive for 1-4 consecutive weeks; in adults the range was 2-15 weeks, with almost half of adults maintaining titres above 0.5 IU/ml for 9 or more consecutive weeks. Based on the kinetics of the antibody response to ONRAB, the best time to sample sera of wild adult foxes for evidence of vaccination is 7-11 weeks following bait distribution. Thirty-four foxes (25 ONRAB, 9 controls) were challenged with vulpine street virus 547 days post-vaccination. All controls developed rabies whereas eight of 13 adult vaccinates (62%) and four of 12 juvenile vaccinates (33%) survived. All foxes classed as non-responders to vaccination developed rabies. Of foxes considered responders to vaccination, 80% of adults (8/10) and 67% of juveniles (4/6) survived challenge. The duration of immunity conferred to foxes would appear adequate for bi-annual and annual bait distribution schedules as vaccinates were challenged 1.5 years post-vaccination.

Ethnicity, detention and early intervention: reducing inequalities and improving outcomes for black and minority ethnic patients: the ENRICH programme, a mixed-methods study

Background

Black and minority ethnic (BME) service users experience adverse pathways into care. Ethnic differences are evident even at first-episode psychosis (FEP); therefore, contributory factors must operate before first presentation to psychiatric services. The ENRICH programme comprised three interlinked studies that aimed to understand ethnic and cultural determinants of help-seeking and pathways to care.

Aims and objectives

Study 1: to understand ethnic differences in pathways to care in FEP by exploring cultural determinants of illness recognition, attribution and help-seeking among different ethnic groups. Study 2: to evaluate the process of detention under the Mental Health Act (MHA) and determine predictors of detention. Study 3: to determine the appropriateness, accessibility and acceptability of generic early intervention services for different ethnic groups.

Methods

Study 1: We recruited a prospective cohort of FEP patients and their carers over a 2-year period and assessed the chronology of symptom emergence, attribution and help-seeking using semistructured tools: the Nottingham Onset Schedule (NOS), the Emerging Psychosis Attribution Schedule and the ENRICH Amended Encounter Form. A stratified subsample of user–carer NOS interviews was subjected to qualitative analyses. Study 2: Clinical and sociodemographic data including reasons for detention were collected for all MHA assessments conducted over 1 year (April 2009–March 2010). Five cases from each major ethnic group were randomly selected for a qualitative exploration of carer perceptions of the MHA assessment process, its outcomes and alternatives to detention. Study 3: Focus groups were conducted with service users, carers, health professionals, key stakeholders from voluntary sector and community groups, commissioners and representatives of spiritual care with regard to the question: ‘How appropriate and accessible are generic early intervention services for the specific ethnic and cultural needs of BME communities in Birmingham?’

Results

There were no ethnic differences in duration of untreated psychosis (DUP) and duration of untreated illness in FEP. DUP was not related to illness attribution; long DUP was associated with patients being young (< 18 years) and living alone. Black patients had a greater risk of MHA detention, more criminal justice involvement and more crisis presentations than white and Asian groups. Asian carers and users were most likely to attribute symptoms to faith-based or supernatural explanations and to seek help from faith organisations. Faith-based help-seeking, although offering comfort and meaning, also risked delaying access to medical care and in some cases also resulted in financial exploitation of this vulnerable group. The BME excess in MHA detentions was not because of ethnicity per se; the main predictors of detention were a diagnosis of mental illness, presence of risk and low level of social support. Early intervention services were perceived to be accessible, supportive, acceptable and culturally appropriate. There was no demand or perceived need for separate services for BME groups or for ethnic matching between users and clinicians.

Conclusions

Statutory health-care organisations need to work closely with community groups to improve pathways to care for BME service users. Rather than universal public education campaigns, researchers need to develop and evaluate public awareness programmes that are specifically focused on BME groups.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

Measuring enamel erosion: a comparative study of contact profilometry, non-contact profilometry and confocal laser scanning microscopy

OBJECTIVES

To compare three instruments for their ability to quantify enamel loss after acid erosion.

METHODS

6 randomized parallel groups of bovine enamel samples were subjected to citric acid (higher acidity) or orange juice (lower acidity) erosion and remineralisation in a cycling model. Two protected shoulders were created on each of the samples using tape, to serve as reference for analysis. The time of exposure to each acid was varied, along with presence or absence of agitation. After treatment, samples were measured on 3 instruments capable of measuring step height: a contact profilometer (CP); a non-contact profilometer (NCP); and a confocal laser scanning microscope (CLSM) by three different examiners. Additionally, 3D (volume) step height was also measured using the CLSM.

RESULTS

Increasing acid concentration and exposure time resulted in greater erosion, as did agitation of samples while in acid solution. All instruments/methods identified the same statistically significant (p<0.05) pair-wise differences between the treatments groups. Further, all four methods exhibited strong agreement (Intra-class correlation ≥ 0.96) in erosion level and were highly correlated, with correlations of 0.99 or higher in all cases.

SIGNIFICANCE

All instruments/methods used in this study produced very similar conclusions with regard to ranking of enamel loss, with data showing very high agreement between instruments. All instruments were found to be equally suited to the measurement of enamel erosion.

Point mutations in the transmembrane region of the clic1 ion channel selectively modify its biophysical properties

Chloride intracellular Channel 1 (CLIC1) is a metamorphic protein that changes from a soluble cytoplasmic protein into a transmembrane protein. Once inserted into membranes, CLIC1 multimerises and is able to form chloride selective ion channels. Whilst CLIC1 behaves as an ion channel both in cells and in artificial lipid bilayers, its structure in the soluble form has led to some uncertainty as to whether it really is an ion channel protein.

CLIC1 has a single putative transmembrane region that contains only two charged residues: arginine 29 (Arg29) and lysine 37 (Lys37). As charged residues are likely to have a key role in ion channel function, we hypothesized that mutating them to neutral alanine to generate K37A and R29A CLIC1 would alter the electrophysiological characteristics of CLIC1. By using three different electrophysiological approaches: i) single channel Tip-Dip in artificial bilayers using soluble recombinant CLIC1, ii) cell-attached and iii) whole-cell patch clamp recordings in transiently transfected HEK cells, we determined that the K37A mutation altered the single-channel conductance while the R29A mutation affected the single-channel open probability in response to variation in membrane potential.

Our results show that mutation of the two charged amino acids (K37 and R29) in the putative transmembrane region of CLIC1 alters the biophysical properties of the ion channel in both artificial bilayers and cells. Hence these charged residues are directly involved in regulating its ion channel activity. This strongly suggests that, despite its unusual structure, CLIC1 itself is able to form a chloride ion channel.

False-positive prostate cancer markers in a man with symptomatic urethral Chlamydia trachomatis infection

Summary

Symptomatic male urethral Chlamydia trachomatis infection resulted in inflammation of the prostate, with associated increases in both prostate-specific (PSA) and prostate cancer-specific (PCA3) markers with prostate biopsies showing no evidence of malignancy.

CLIC proteins, ezrin, radixin, moesin and the coupling of membranes to the actin cytoskeleton: a smoking gun?

The CLIC proteins are a highly conserved family of metazoan proteins with the unusual ability to adopt both soluble and integral membrane forms. The physiological functions of CLIC proteins may include enzymatic activity in the soluble form and anion channel activity in the integral membrane form. CLIC proteins are associated with the ERM proteins: ezrin, radixin and moesin. ERM proteins act as cross-linkers between membranes and the cortical actin cytoskeleton. Both CLIC and ERM proteins are controlled by Rho family small GTPases. CLIC proteins, ERM and Rho GTPases act in a concerted manner to control active membrane processes including the maintenance of microvillar structures, phagocytosis and vesicle trafficking. All of these processes involve the interaction of membranes with the underlying cortical actin cytoskeleton. The relationships between Rho GTPases, CLIC proteins, ERM proteins and the membrane:actin cytoskeleton interface are reviewed. Speculative models are proposed involving the formation of localised multi-protein complexes on the membrane surface that assemble via multiple weak interactions. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.

Effects of calcium binding and the hypertrophic cardiomyopathy A8V mutation on the dynamic equilibrium between closed and open conformations of the regulatory N-domain of isolated cardiac troponin C

Troponin C (TnC) is the calcium-binding subunit of the troponin complex responsible for initiating striated muscle contraction in response to calcium influx. In the skeletal TnC isoform, calcium binding induces a structural change in the regulatory N-domain of TnC that involves a transition from a closed to open structural state and accompanying exposure of a large hydrophobic patch for troponin I (TnI) to subsequently bind. However, little is understood about how calcium primes the N-domain of the cardiac isoform (cTnC) for interaction with the TnI subunit as the open conformation of the regulatory domain of cTnC has been observed only in the presence of bound TnI. Here we use paramagnetic relaxation enhancement (PRE) to characterize the closed to open transition of isolated cTnC in solution, a process that cannot be observed by traditional nuclear magnetic resonance methods. Our PRE data from four spin-labeled monocysteine constructs of isolated cTnC reveal that calcium binding triggers movement of the N-domain helices toward an open state. Fitting of the PRE data to a closed to open transition model reveals the presence of a small population of cTnC molecules in the absence of calcium that possess an open conformation, the level of which increases substantially upon Ca(2+) binding. These data support a model in which calcium binding creates a dynamic equilibrium between the closed and open structural states to prime cTnC for interaction with its target peptide. We also used PRE data to assess the structural effects of a familial hypertrophic cardiomyopathy point mutation located within the N-domain of cTnC (A8V). The PRE data show that the Ca(2+) switch mechanism is perturbed by the A8V mutation, resulting in a more open N-domain conformation in both the apo and holo states.

Three-dimensional optical manipulation of a single electron spin

Nitrogen vacancy (NV) centres in diamond are promising elemental blocks for quantum optics, spin-based quantum information processing and high-resolution sensing. However, fully exploiting the capabilities of these NV centres requires suitable strategies to accurately manipulate them. Here, we use optical tweezers as a tool to achieve deterministic trapping and three-dimensional spatial manipulation of individual nanodiamonds hosting a single NV spin. Remarkably, we find that the NV axis is nearly fixed inside the trap and can be controlled in situ by adjusting the polarization of the trapping light. By combining this unique spatial and angular control with coherent manipulation of the NV spin and fluorescence lifetime measurements near an integrated photonic system, we demonstrate individual optically trapped NV centres as a novel route for both three-dimensional vectorial magnetometry and sensing of the local density of optical states.

Interdomain orientation of cardiac troponin C characterized by paramagnetic relaxation enhancement NMR reveals a compact state

Cardiac troponin C (cTnC) is the calcium binding subunit of the troponin complex that triggers the thin filament response to calcium influx into the sarcomere. cTnC consists of two globular EF-hand domains (termed the N- and C-domains) connected by a flexible linker. While the conformation of each domain of cTnC has been thoroughly characterized through NMR studies involving either the isolated N-domain (N-cTnC) or C-domain (C-cTnC), little attention has been paid to the range of interdomain orientations possible in full-length cTnC that arises as a consequence of the flexibility of the domain linker. Flexibility in the domain linker of cTnC is essential for effective regulatory function of troponin. We have therefore utilized paramagnetic relaxation enhancement (PRE) NMR to assess the interdomain orientation of cTnC. Ensemble fitting of our interdomain PRE measurements reveals that isolated cTnC has considerable interdomain flexibility and preferentially adopts a bent conformation in solution, with a defined range of relative domain orientations.

Intracellular chloride channel protein CLIC1 regulates macrophage function through modulation of phagosomal acidification

Intracellular chloride channel protein 1 (CLIC1) is a 241 amino acid protein of the glutathione S transferase fold family with redox- and pH-dependent membrane association and chloride ion channel activity. Whilst CLIC proteins are evolutionarily conserved in Metazoa, indicating an important role, little is known about their biology. CLIC1 was first cloned on the basis of increased expression in activated macrophages. We therefore examined its subcellular localisation in murine peritoneal macrophages by immunofluorescence confocal microscopy. In resting cells, CLIC1 is observed in punctate cytoplasmic structures that do not colocalise with markers for endosomes or secretory vesicles. However, when these macrophages phagocytose serum-opsonised zymosan, CLIC1 translocates onto the phagosomal membrane. Macrophages from CLIC1(-/-) mice display a defect in phagosome acidification as determined by imaging live cells phagocytosing zymosan tagged with the pH-sensitive fluorophore Oregon Green. This altered phagosomal acidification was not accompanied by a detectable impairment in phagosomal-lysosomal fusion. However, consistent with a defect in acidification, CLIC1(-/-) macrophages also displayed impaired phagosomal proteolytic capacity and reduced reactive oxygen species production. Further, CLIC1(-/-) mice were protected from development of serum transfer induced K/BxN arthritis. These data all point to an important role for CLIC1 in regulating macrophage function through its ion channel activity and suggest it is a suitable target for the development of anti-inflammatory drugs.

Developing dietetic positions in rural areas: what are the key lessons?

INTRODUCTION

Rural and remote communities in Australia are typically underserviced by dietitians. The recruitment of dietitians to rural areas has improved in recent years; however, retention remains an issue. Key factors that lead to an increase in funding and the development of more dietetic positions in rural areas are unknown. The purpose of this study was to describe dietetic services in rural areas and to determine the drivers for and barriers to the development of dietetic positions in rural areas.

METHODS

A sequential explanatory mixed methods approach was used to examine six case study sites of dietetic service delivery in rural northern New South Wales (NSW) Australia between 1991 and 2006. The six sites represented different models of dietetic service delivery from the study area. Data sources included workforce documents and in-depth individual interviews on position development with 40 key informants, including past and present dietitians, dietetic managers and health service managers. Interview data were thematically analysed with the aid of NVivo7 (www.qsrinternational.com). Themes were coded into common categories, using a constant comparison inductive approach.

RESULTS

Forty key informants agreed to participate in the in-depth, semi-structured interview. Participants included 28 dietitians (past and present), three dietetics managers and nine managers. The majority of participants were female (87.5%). Document analysis showed that the dietetic workforce had a 5.6-fold increase across the six sites over the 15 years. Themes that emerged from the interviews indicated that new positions were established through ad hoc and opportunistic funding, a gradual increase in funding or due to concerted efforts by champions advocating for increased funding.

CONCLUSION

The findings from this study have important implications for the development of dietetic staffing in rural areas. There is an inconsistent approach to the development of dietetic positions in rural areas of Australia. Factors that inhibited the development of positions included a general lack of funds and competing priorities. A systematic, planned approach to the development of dietetic positions is needed in rural Australia. Champions for the development of positions were effective in increasing positions, particularly when they have management support.

Processing 15-nm Nanodiamonds Containing Nitrogen-vacancy Centres for Single-molecule FRET

Colour centres in nanodiamonds have many properties such as chemical and physical stability, biocompatibility, straightforward surface functionalisation as well as bright and stable photoluminescence, which make them attractive for biological applications. Here we examine the use of fluorescent nanodiamonds containing a single nitrogen-vacancy (NV) centre, as an alternative nano-label over conventional fluorophores. We describe a series of chemical treatments and air oxidation to reliably produce small (~15 nm) oxidised nanodiamonds suitable for applications in bioscience. We use Förster resonance energy transfer to measure the coupling efficiency from a single NV centre in a selected nanodiamond to an IRDye 800CW dye molecule absorbed onto the surface. Our single-molecule Förster resonance energy transfer analysis, based on fluorescence lifetime measurements, locates the position of the photostable NV centre deep within the core of the nanodiamond.

Transmembrane extension and oligomerization of the CLIC1 chloride intracellular channel protein upon membrane interaction

Chloride intracellular channel proteins (CLICs) differ from most ion channels as they can exist in both soluble and integral membrane forms. The CLICs are expressed as soluble proteins but can reversibly autoinsert into the membrane to form active ion channels. For CLIC1, the interaction with the lipid bilayer is enhanced under oxidative conditions. At present, little evidence is available characterizing the structure of the putative oligomeric CLIC integral membrane form. Previously, fluorescence resonance energy transfer (FRET) was used to monitor and model the conformational transition within CLIC1 as it interacts with the membrane bilayer. These results revealed a large-scale unfolding between the C- and N-domains of CLIC1 as it interacts with the membrane. In the present study, FRET was used to probe lipid-induced structural changes arising in the vicinity of the putative transmembrane region of CLIC1 (residues 24-46) under oxidative conditions. Intramolecular FRET distances are consistent with the model in which the N-terminal domain inserts into the bilayer as an extended α-helix. Further, intermolecular FRET was performed between fluorescently labeled CLIC1 monomers within membranes. The intermolecular FRET shows that CLIC1 forms oligomers upon oxidation in the presence of the membranes. Fitting the data to symmetric oligomer models of the CLIC1 transmembrane form indicates that the structure is large and most consistent with a model comprising approximately six to eight subunits.

Structural gymnastics of multifunctional metamorphic proteins

The classic structure-function paradigm holds that a protein exhibits a single well-defined native state that gives rise to its biological function. Nonetheless, over the past few decades, numerous examples of proteins exhibiting biological function arising from multiple structural states of varying disorder have been identified. Most recently, several examples of 'metamorphic proteins', able to interconvert between vastly different native-like topologies under physiological conditions, have been characterised with multiple functions. In this review, we look at the concept of protein metamorphosis in relation to the current understanding of the protein structure-function landscape. Although structural dynamism observed for metamorphic proteins provides a novel source of functional versatility, the dynamic nature of the metamorphic proteins generally makes them difficult to identify and probe using conventional protein structure determination methods. However, as the existence of metamorphic proteins has now been established and techniques enabling the analysis of multiple protein conformers are improving, it is likely that this class will continue to grow in number.

Distance measurements by continuous wave EPR spectroscopy to monitor protein folding

Site-Directed Spin Labeling Electron Paramagnetic Resonance (SDSL-EPR) offers a powerful method for the structural analysis of protein folds. This method can be used to test and build secondary, tertiary, and quaternary structural models as well as measure protein conformational changes in solution. Insertion of two cysteine residues into the protein backbone using molecular biology methods and the subsequent labeling of the cysteine residues with a paramagnetic spin label enables the technique of EPR to be used as a molecular spectroscopic ruler. EPR measures the dipolar interaction between pairs of paramagnetic spin labels to yield internitroxide distances from which quantitative structural information on a protein fold can then be obtained. Interspin dipolar interaction between two spin labels at less than 25  Å are measured using continuous wave (CW) EPR methods. As for any low-resolution distance methods, the positioning of the spin labels and the number of distance constraints to be measured are dependent on the structural question being asked, thus a pattern approach for using distance sets to decipher structure mapping, including protein folds and conformational changes associated with biological activity, is essential. Practical guidelines and hints for the technique of SDSL-EPR are described in this chapter, including methods for spin labeling the protein backbone, CW-EPR data collection at physiological temperatures and two semiquantitative analysis methods to extract interspin distance information from the CW-EPR spectra.

Miniaturized ultra high field asymmetric waveform ion mobility spectrometry combined with mass spectrometry for peptide analysis

Miniaturized ultra high field asymmetric waveform ion mobility spectrometry (ultra-FAIMS) combined with mass spectrometry (MS) has been applied to the analysis of standard and tryptic peptides, derived from α-1-acid glycoprotein, using electrospray and nanoelectrospray ion sources. Singly and multiply charged peptide ions were separated in the gas phase using ultra-FAIMS and detected by ion trap and time-of-flight MS. The small compensation voltage (CV) window for the transmission of singly charged ions demonstrates the ability of ultra-FAIMS-MS to generate pseudo-peptide mass fingerprints that may be used to simplify spectra and identify proteins by database searching. Multiply charged ions required a higher CV for transmission, and ions with different amino acid sequences may be separated on the basis of their differential ion mobility. A partial separation of conformers was also observed for the doubly charged ion of bradykinin. Selection on the basis of charge state and differential mobility prior to tandem mass spectrometry facilitates peptide and protein identification by allowing precursor ions to be identified with greater selectivity, thus reducing spectral complexity and enhancing MS detection.

Metamorphic response of the CLIC1 chloride intracellular ion channel protein upon membrane interaction

A striking feature of the CLIC (chloride intracellular channel) protein family is the ability of its members to convert between a soluble state and an integral membrane channel form. Direct evidence of the structural transition required for the CLIC protein to autonomously insert into the membrane is lacking, largely because of the challenge of probing the conformation of the membrane-bound protein. However, insights into the CLIC transmembrane form can be gained by biophysical methods such as fluorescence resonance energy transfer (FRET) spectroscopy. This approach was used to measure distances from tryptophan 35, located within the CLIC1 putative N-domain transmembrane region, to three native cysteine residues within the C-terminal domain. These distances were computed both in aqueous solution and upon the addition of membrane vesicles. The FRET distances were used as constraints for modeling of a structure for the CLIC1 integral membrane form. The data are suggestive of a large conformational unfolding occurring between the N- and C-domains of CLIC1 upon interaction with the membrane. Consistent with previous findings, the N-terminal domain of CLIC1 is likely to insert into the lipid bilayer, while the C-domain remains in solution on the extravesicular side of the membrane.

Observation and control of blinking nitrogen-vacancy centres in discrete nanodiamonds

Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics, nanoscale magnetometry and biolabelling. Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds and milled nanodiamonds, they have not been observed in very small isolated nanodiamonds. Here, we report the first direct observation of nitrogen-vacancy centres in discrete 5-nm nanodiamonds at room temperature, including evidence for intermittency in the luminescence (blinking) from the nanodiamonds. We also show that it is possible to control this blinking by modifying the surface of the nanodiamonds.

Generation and characterization of mice with null mutation of the chloride intracellular channel 1 gene

CLIC1 belongs to a family of highly conserved and widely expressed intracellular chloride ion channel proteins existing in both soluble and membrane integrated forms. To study the physiological and biological role of CLIC1 in vivo, we undertook conditional gene targeting to engineer Clic1 gene knock-out mice. This represents creation of the first gene knock-out of a vertebrate CLIC protein family member. We first generated a Clic1 Knock-in (Clic1(FN)) allele, followed by Clic1 knock-out (Clic1(-/-)) mice by crossing Clic1(FN) allele with TNAP-cre mice, resulting in germline gene deletion through Cre-mediated recombination. Mice heterozygous or homozygous for these alleles are viable and fertile and appear normal. However, Clic1(-) (/-) mice show a mild platelet dysfunction characterized by prolonged bleeding times and decreased platelet activation in response to adenosine diphosphate stimulation linked to P2Y(12) receptor signaling.

The enigma of the CLIC proteins: Ion channels, redox proteins, enzymes, scaffolding proteins?

Chloride intracellular channel proteins (CLICs) are distinct from most ion channels in that they have both soluble and integral membrane forms. CLICs are highly conserved in chordates, with six vertebrate paralogues. CLIC-like proteins are found in other metazoans. CLICs form channels in artificial bilayers in a process favoured by oxidising conditions and low pH. They are structurally plastic, with CLIC1 adopting two distinct soluble conformations. Phylogenetic and structural data indicate that CLICs are likely to have enzymatic function. The physiological role of CLICs appears to be maintenance of intracellular membranes, which is associated with tubulogenesis but may involve other substructures.