Adhesion of microbes using 3-aminopropyl triethoxy silane and specimen stabilisation techniques for analytical transmission electron microscopy

Studies of Surface Preparation for the Fluorosequencing of Peptides

Silica passivating agents have shown great success in minimizing nonspecific protein binding to glass surfaces for imaging and microscopy applications. Amine-derivatized surfaces are commonly used in conjugation with amide coupling agents to immobilize peptides/proteins through C-terminal or side-chain carboxylic acids. In the case of the single-molecule fluorosequencing of peptides, attachment occurs via the C-terminus and nonspecific surface binding has previously been a source of error in peptide identification. Here, we employ fluorosequencing as a high-throughput, single-molecule sensitivity assay to identify and quantify the extent of nonspecific binding of peptides to amine-derivatized surfaces. We show that there is little improvement when using common passivating agents in combination with the surface derivatizing agent 3-aminopropyl-triethoxysilane (APTES) to couple the peptides to the modified surface. Furthermore, many xanthene fluorophores have carboxylic acids in the appended phenyl ring at positions ortho and meta or ortho and para, and the literature shows that conjugation through the ortho position is not favored. Because xanthene-derived fluorophores are commonly used for single-molecule applications, we devised a novel assay to probe the conjugation of peptides via their fluorophores relative to their C-termini on silane-derivatized surfaces. We find significant attachment to the ortho position, which is a warning to those attempting to immobilize fluorophore-labeled peptides to silica surfaces via amide coupling agents. However, eliminating all amines on the surface by switching to 3-azidopropyl-triethoxysilane (AzTES) for coupling via copper-catalyzed azide-alkyne cycloaddition (CuAAC) and omitting additional passivation agents allowed us to achieve a high level of C-terminally bound peptides relative to nonspecifically or ortho-phenyl-bound, fluorophore-labeled peptides. This strategy substantially improves the specificity of peptide immobilization for single-molecule fluorosequencing experiments.

Intermediate-Risk Chronic Stable Angina: Neutrophil-Lymphocyte Ratio and Fibrinogen Levels Improved Predicting Angiographically-Detected Coronary Artery Disease

BACKGROUND

Coronary heart disease (CHD) is the leading cause of death worldwide. Research indicates that coronary atherosclerosis is the most frequent cause of CHD. Evidence is scarce concerning the clinical efficacy of fibrinogen or neutrophil-lymphocyte ratio (NLR) measurement in risk-stratifying patients with chronic stable angina.

OBJECTIVES

To examine the independent and incremental prognostic value of fibrinogen and neutrophil-lymphocyte ratio (NLR) for angiographically-detected coronary artery disease (CAD).

PATIENTS AND METHODS

In this cross-sectional study, angiography was performed for 183 Iranian patients with chronic stable angina with exercise ECG-determined intermediate risk. Generalized estimated equations were used to obtain the odd ratio (OR) of CAD for a 1-unit increase in log-NLR and a 1-SD increase in plasma fibrinogen. Models were adjusted for established CAD risk factors. Integrated discriminatory improvement index (IDI) and net reclassification improvement index (NRI) were used as measures of predictive ability for CAD, combined with traditional risk factors by NLR and fibrinogen.

RESULTS

The mean age of the participants was 57.5, with 51.9% being male. Only 12% of participants had angiographically-determined patent coronary arteries. The number of participants with one, two, and three-vessel stenosis were 76, 31, 31, respectively, while 45 did not have stenosed vessels. NLR and fibrinogen levels were significantly higher in patients with stenosis in two (2.4 and 512 mg.dL^-1) or three (2.6 and 517 mg.dL^-1) coronary arteries, as compared to the group of patients with no significant involvement (2 and 430 mg.dL^-1) (all P < 0.01). Patients with a higher NLR and a higher fibrinogen levels were more likely to have higher grades of CAD. OR log-NLR = 1.36 (95% CI: 1.05 - 1.94) and OR Z-Fibrinogen = 1.61 (95% CI: 1.18 - 2.22). When NLR and fibrinogen were added to the traditional risk factors separately, the NRIs were 0.170 (0.023 - 0.324) and 0.380 (0.214 - 0.543), respectively. The NRI was 0.460 (0.303 - 0.620) when both NLR and fibrinogen added to traditional risk factors simultaneously.

CONCLUSIONS

NLR and fibrinogen predicted CAD, independent of traditional CAD risk factors. Both measures (whether separately or together) substantially enhanced the predictive performance of traditional risk factors for identifying patients with CAD.

Deferasirox loaded on fumed silica nanoparticles used in cancer treatment

Fumed silica nanoparticles loaded with deferasirox are three and five times more cytotoxic than cisplatin and deferasirox against MDA-MB-23, respectively.

Deferasirox-coated iron oxide nanoparticles as a potential cytotoxic agent

Two broad strategies for the use of iron chelators in cancer treatment have been explored.

Covalent immobilization of microtubules on glass surfaces for molecular motor force measurements and other single-molecule assays

Rigid attachment of microtubules (MTs) to glass cover slip surfaces is a prerequisite for a variety of microscopy experiments in which MTs are used as substrates for MT-associated proteins, such as the molecular motors kinesin and cytoplasmic dynein. We present an MT-surface coupling protocol in which aminosilanized glass is formylated using the cross-linker glutaraldehyde, fluorescence-labeled MTs are covalently attached, and the surface is passivated with highly pure beta-casein. The technique presented here yields rigid MT immobilization while simultaneously blocking the remaining glass surface against nonspecific binding by polystyrene optical trapping microspheres. This surface chemistry is straightforward and relatively cheap and uses a minimum of specialized equipment or hazardous reagents. These methods provide a foundation for a variety of optical tweezers experiments with MT-associated molecular motors and may also be useful in other assays requiring surface-immobilized proteins.

Attachment of 3-(Aminopropyl)triethoxysilane on silicon oxide surfaces: dependence on solution temperature

Parameters important to the self-assembly of 3-(aminopropyl)triethoxysilane (APTES) on chemically grown silicon oxide (SiO 2) to form an aminopropyl silane (APS) film have been investigated using in situ infrared (IR) absorption spectroscopy. Preannealing to approximately 70 degrees C produces significant improvements in the quality of the film: the APS film is denser, and the Si-O-Si bonds between the molecules and the SiO 2 surface are more structured and ordered with only a limited number of remaining unreacted ethoxy groups. In contrast, post-annealing the functionalized SiO 2 samples after room temperature reaction with APTES (i.e., ex situ annealing) does not lead to any spectral change, suggesting that post-annealing has no strong effect on the horizontal polymerization as suggested earlier. Both IR and ellipsometry data show that the higher the solution temperature, the denser and thinner the APS layer is for a given immersion time. Finally, the APS layer obtained by preannealing the solution at 70 degrees C exhibits a better stability in deionized water than the APS layer prepared at room temperature.

Magnetosomal matrix: ultrafine structure may template biomineralization of magnetosomes

The organic matrix surrounding bullet-shaped, cubo-octahedral, D-shaped, irregular arrowhead-shaped, and truncated hexa-octahedral magnetosomes was analysed in a variety of uncultured magnetotactic bacteria. The matrix was examined using low- (80 kV) and intermediate- (400 kV) voltage TEM. It encapsulated magnetosomes in dehydrated cells, ultraviolet-B-irradiated dehydrated cells and stained resin-embedded fixed cells, so the apparent structure of the matrix does not appear to be an artefact of specimen preparation. High-resolution images revealed lattice fringes in the matrix surrounding magnetite and greigite magnetosomes that were aligned with lattice fringes in the encapsulated magnetosomes. In all except one case, the lattice fringes had widths equal to or twice the width of the corresponding lattice fringes in the magnetosomes. The lattice fringes in the matrix were aligned with the [311], [220], [331], [111] and [391] related lattice planes of magnetite and the [222] lattice plane of greigite. An unidentified material, possibly an iron hydroxide, was detected in two immature magnetosomes containing magnetite. The unidentified phase had a structure similar to that of the matrix as it contained [311], [220] and [111] lattice fringes, which indicates that the matrix acts as a template for the spatially controlled biomineralization of the unidentified phase, which itself transforms into magnetite. The unidentified phase was thus called pre-magnetite. The presence of the magnetosomal matrix explains all of the five properties of the biosignature of the magnetosomal chain proposed previously by Friedmann et al. and supports their claim that some of the magnetite particles in the carbonate globules in the Martian meteorite ALH84001 are biogenic. Two new morphologies of magnetite magnetosomes are also reported here (i.e. tooth-shaped and hexa-octahedral magnetosomes). Tooth-shaped magnetite magnetosomes elongated in the [110] direction are reported, and are distinct from arrowhead-shaped and bullet-shaped magnetosomes. Elongation of magnetite magnetosomes in the [110] direction has not been reported previously. A Martian hexa-octahedral magnetite particle was previously characterized by Thomas-Keptra et al. and compared with truncated hexa-octahedral magnetite magnetosomes. Hexa-octahedral magnetite magnetosomes with the same morphology and similar sizes and axial ratios as those reported by Thomas-Keptra et al. are characterized here. These observations support their claim that ALH84001 contains evidence for a past Martian biota.