Active CRISPR-Cas12a on Hydrophilic Metal-Organic Frameworks: A Nanobiocomposite with High Stability and Activity for Nucleic Acid Detection

CRISPR-Cas12a is an accurate and responsive biosensing technique, but its limited stability has restricted its widespread applications. To address this, we propose a strategy using metal-organic frameworks (MOFs) to protect Cas12a from harsh environments. After screening multiple candidate MOFs, it was found that hydrophilic MAF-7 is highly compatible with Cas12a, and the as-formed Cas12a-on-MAF-7 (COM) not only retains high enzymatic activity but also possesses excellent tolerance to heat, salt, and organic solvents. Further investigation showed that COM can serve as an analytical component for nucleic acid detection, resulting in an ultrasensitive assay for SARS-CoV-2 RNA detection with a detection limit of 1 copy. This is the first successful attempt to create an active Cas12a nanobiocomposite that functions as a biosensor without the need for shell deconstruction or enzyme release.

Integrating CRISPR/Cas12a with strand displacement amplification for the ultrasensitive aptasensing of cadmium(II)

Cadmium ion (Cd(II)) is a pernicious environmental pollutant that has been shown to contaminate agricultural lands, accumulate through the food chain, and seriously threaten human health. At present, Cd(II) monitoring is dependent on centralized instruments, necessitating the development of rapid and on-site detection platforms. Against this backdrop, the present study reports on the development of a fluorometric aptasensor designed to target Cd(II), which is achieved through the integration of strand displacement amplification (SDA) and CRISPR/Cas12a. In the absence of Cd(II), the aptamer initiates SDA, resulting in the generation of a profusion of ssDNA that activates Cas12a, leading to a substantial increase in fluorescence output. Conversely, the presence of Cd(II) curtails the SDA efficiency, culminating in a significant reduction in fluorescence output. The proposed approach has been demonstrated to enable the selective detection of Cd(II) at concentrations of 60 pM, with the performance of the aptasensor validated in real water and rice samples. The proposed platform based on aptamer-target interaction holds immense promise as a signal-amplified and precise method for the detection of Cd(II) and has the potential to transform current hazard detection practices in food samples.

The DNA-Cu nanocluster and exonuclease I integrated label-free reporting system for CRISPR/Cas12a-based SARS-CoV-2 detection with minimized background signal

CRISPR-driven biosensing is developing rapidly, but current works mostly adopt dye-labeled ssDNA as the signal reporter, which is costly and unstable. Herein, we developed a label-free and low-background reporter for...

Design of super-strong and thermally stable nanotwinned Al alloys via solute synergy

Al alloys have widespread industrial applications. However, their mechanical strength is often much lower than steels. Here, we investigate the influence of solutes on achieving ultrahigh strength and thermal stability of nanotwinned Al alloys. In situ micropillar compression tests show the addition of a small amount of Ti can significantly increase the mechanical strength of Al-Ni alloys to 2 GPa. Deformation induced detwinning, Ni segregation and grain coarsening as discovered in binary Al-Ni alloys are mostly absent in the ternary Al-Ni-Ti alloys. Moreover, the ternary Al-Ni-Ti alloys have outstanding thermal stability. Density function theory calculations reveal the synergetic pinning effect of Ni-Ti solute pairs on incoherent twin boundaries. This study demonstrates that the proper selection of synergistic solute pairs is critical to improve the thermal stability and mechanical properties of nanotwinned Al alloys.

3D Co-culture of Cancer-Associated Fibroblast with Oral Cancer Organoids

Limits of the available model have, in the long term, challenged the studies of cancer-associated fibroblasts (CAFs) and their interplay with cancer stem cells, one of the key driving forces of patients with oral squamous cell carcinoma (OSCC). In the present study, the 3-dimensional organoid model was employed to investigate whether co-culture with paralleled CAFs promotes stem-like properties of OSCC. Experimentally, tumor organoids and paralleled CAFs were generated from patients with OSCC. Then, the CD44⁺ cells in organoids were sorted out by flow cytometry and co-cultured with CAFs in Matrigel. The results showed that co-culture with CAFs enhances the organoid-forming ability of CD44⁺ cells and that this effect was blocked when production or uptake of lactate in CAFs or CD44⁺ cells was inhibited. Furthermore, the expression levels of CD44 and OCT-4 were detected in organoids incubated with lactate, via immunofluorescence or Western blot assay. The results demonstrated that treatments with lactate promote the organoid-forming ability of CD44⁺ cells, as well as the expression of CD44 and OCT-4 at the protein level in OSCC organoids.

Intraspecific Diversity and Taxonomy of Emmonsia crescens

Emmonsia crescens is known as an environmental pathogen causing adiaspiromycosis in small rodents. As the generic name Emmonsia is no longer available for this species, its taxonomic position is re-evaluated. The intraspecific variation of Emmonsia crescens was analyzed using molecular, morphological, and physiological data, and the relationship between frequency of adiaspiromycosis and body temperature of host animals was explored. A North American and a pan-global lineage could be discerned, each with subclusters at low genetic distance. European strains produced the classical type of very large adiaspores, while in the North American lineage adiaspores relatively small, resembling the broad-based budding cells of Blastomyces. Members of the closely related genus Emergomyces may exhibit large, broad-based in addition to small, narrow-based budding cells. We conclude that the morphology of the pathogenic phase in these fungi differs gradationally between species and even populations, and is therefore less suitable as a diagnostic criterion for generic delimitation. Two Emmonsia species are reclassified in Emergomyces.

Thick grain boundary induced strengthening in nanocrystalline Ni alloy

Grain refinement has been extensively used to strengthen metallic materials for decades. Grain boundaries act as effective barriers to the transmission of dislocations, consequently leading to strengthening. Conventional grain boundaries have a thickness of 1-2 atomic layers, typically ∼0.5 nm for most metallic materials. Here, we report, however, the formation of ∼3 nm thick grain boundaries in a nanocrystalline Ni alloy. In situ micropillar compression studies coupled with molecular dynamics simulations suggest that the thick grain boundaries are stronger barriers than conventional grain boundaries to the transmission of dislocations. This study provides a fresh perspective for the design of high strength, deformable nanostructured metallic materials.

Mandibular reconstruction using the deep circumflex iliac artery free flap: effect of the length of bone harvested on donor site morbidity

The aim of this study was to assess the amounts of pain and morbidity that are associated with the length of the harvested anterior iliac bone graft (cm), and their effect on the contour of the donor site and activities of daily life. A total of 62 patients who had mandibular reconstruction using an iliac bone graft were enrolled in this study at the Wuhan University Hospital. The same surgical standards were used throughout. We divided the patients into two groups depending to the length of the graft (<9cm or 9cm or more). The amount and duration of the pain, the time necessary to walk normally, abnormalities of sensation, contour of the donor site, length of the scar, and the patients' satisfaction with the donor site were evaluated, and outcomes in the two groups compared. The worst pain after operation (p=0.001) the length of the scar (p=0.001), and the time needed before the patients were able to walk (p=0.001) differed significantly between the two groups. There was no significant difference between the two groups regarding other complications. The anterior iliac crest might still be considered to be an ideal donor site for large mandibular defects.

Targeting the overexpressed ROC1 induces G2 cell cycle arrest and apoptosis in esophageal cancer cells

Recent reports showed that regulator of Cullins-1 (ROC1) play an important role in tumor progression in a tumor-specific manner. However, the role and mechanism of ROC1 in esophageal cancer remains elusive. Here we demonstrated that ROC1 was overexpressed in esophageal squamous cell carcinomas, which was positive associated with poor prognosis of esophageal cancer patients. ROC1 knockdown significantly inhibited the growth of esophageal cancer cells in vitro and in vivo. Mechanistically, ROC1 silencing induced G2 cell cycle arrest and triggered apoptosis by accumulating the pro-apoptotic protein NOXA. Consistently, the downregulation of NOXA expression via siRNA substantially attenuated apoptosis induced by ROC1 silencing. These findings suggest that ROC1 is an appealing drug target for esophageal cancer.

Neddylation inhibitor MLN4924 induces G2 cell cycle arrest, DNA damage and sensitizes esophageal squamous cell carcinoma cells to cisplatin

Inhibiting the protein neddylation pathway using the NEDD8-activating enzyme inhibitor MLN4924 represents an attractive anticancer strategy having been demonstrated to exhibit promising anticancer efficacy and with tolerable levels of toxicity; however, the mechanism by which MLN4924 inhibits cell proliferation in human esophageal squamous cell carcinoma (ESCC) cells requires further investigation. The present study revealed that MLN4924 treatment led to G₂ cell cycle arrest and enhanced the protein stability of Wee1-like protein kinase and cyclin dependent protein kinase inhibitor 1A and B and p27. Furthermore, MLN4924 induced DNA damage and sensitized esophageal cancer cells to cisplatin by enhancing apoptosis. These findings extend the understanding of the function and mechanism of MLN4924 in ESCC and provide further evidence for the future development of neddylation inhibitors in clinical trials of esophageal cancer therapy, either alone or in combination.

Adiponectin inhibits oxidization-induced differentiation of T helper cells through inhibiting costimulatory CD40 and CD80

Adiponectin is a multifunctional adipokine that has several oligomeric forms in the blood stream, which broadly regulates innate and acquired immunity. Therefore, in this study, we aimed to observe the differentiation of T helper (Th) cells and expression of costimulatory signaling molecules affected by adiponectin. The mRNA and protein expression levels of adiponectin and its receptors in oxidized low density lipoprotein cholesterol-treated endothelial cells were assayed by real time PCR and immunofluorescence. The endothelial cells were then treated with adiponectin with or without adipoR1 or adipoR2 siRNA and co-cultured with T lymphocytes. The distribution of Th1, Th2 and Th17 subsets were assayed by flow cytometry. The effects of adiponectin on costimulatory signaling molecules HLA-DR, CD80, CD86 and CD 40 was also assayed by flow cytometry. The results showed that endothelial cells expressed adiponectin and its receptor adipoR1 and adipoR2, but not T-cadherin. Adiponectin suppressed Th1 and Th17 differentiation through adipoR1 receptor, contributed to the inhibition of CD80 and CD40, and inhibited differentiation of Th1 and Th17 by inhibiting antigen presenting action.

Assessment of heavy metals in surface sediments from Gansu section of Yellow River, China

The concentrations of Cu, Fe, Mn, Ni, Zn, Cr, Pb, and Cd in 28 samples collected from bottom sediments in the Gansu section of Yellow River, China, were investigated in order to evaluate their distribution and pollution level. The measured metals in the sediments were found to be in the range of Cu 15.52∼57.50 mg/kg, Fe 19593.24∼69963.42 mg/kg, Mn 472.70∼1491.67 mg/kg, Ni 5.10∼74.28 mg/kg, Zn 64.61∼173.83 mg/kg, Cr 57.68∼183.47 mg/kg, Pb 1.21∼28.36 mg/kg, and Cd 0.35∼4.25 mg/kg. The mean values of the heavy metal contents were arranged in the following decreasing order: Fe > Mn > Cr > Zn > Ni > Cu > Pb > Cd. There were significantly positive correlations between Cu, Fe, Mn, and Zn. However, principal component analysis (PCA) extracted two factors with Eigenvalues explaining 62.15 % of the total variance. Cu, Fe, Mn, Zn, and Cr had a natural origin controlled by the first factor. Ni and Pb could originate anthropogenic sources controlled by the second factor. Cd could be affected by natural geological background and human activity. It was attributed principally to anthropogenic activities that the geo-accumulation index, enrichment factor, and pollution load index of Cr were all higher than other measured metals. Zn appears to pose no risk at all of the sites of the system. The pollution class of sediment from the Gansu section in the upstream of Yellow River was 0∼1, from unpolluted to moderately polluted degree.

DNA-PKcs activates the Chk2-Brca1 pathway during mitosis to ensure chromosomal stability

The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is known to have a critical role in DNA double-strand break repair. We have previously reported that DNA-PKcs is activated when cells enter mitosis and functions in mitotic spindle assembly and chromosome segregation. Here we report that DNA-PKcs is the upstream regulator of the Chk2-Brca1 pathway, which impacts microtubule dynamics, kinetochore attachment and chromosomal segregation in mitosis. Downstream from Chk2, Brca1 promotes monoubiquitination of γ-tubulin to inhibit microtubule nucleation and growth. We found that DNA-PKcs is essential for mitotic Chk2 phosphorylation at Thr68. As in Chk2- and Brca1-deficient cells, loss of DNA-PKcs resulted in chromosome misalignment and lagging during anaphase owing to elevation in microtubule dynamics. Importantly, these mitotic aberrations in DNA-PKcs-defective cells were alleviated by the overexpression of phosphomimetic Chk2 or Brca1 mutant proteins but not their wild-type counterparts. Taken together, these results demonstrate that DNA-PKcs regulates mitotic spindle organization and chromosomal instability via the Chk2-Brca1 signaling pathway.

Proposal for new best estimates of the soil-to-plant transfer factor of U, Th, Ra, Pb and Po

There is increasing interest in radiological assessment of discharges of naturally occurring radionuclides into the terrestrial environment. Such assessments require parameter values for the pathways considered in predictive models. An important pathway for human exposure is via ingestion of food crops and animal products. One of the key parameters in environmental assessment is therefore the soil-to-plant transfer factor to food and fodder crops. The objective of this study was to compile data, based on an extensive literature survey, concerning soil-to-plant transfer factors for uranium, thorium, radium, lead, and polonium. Transfer factor estimates were presented for major crop groups (Cereals, Leafy vegetables, Non-leafy vegetables, Root crops, Tubers, Fruits, Herbs, Pastures/grasses, Fodder), and also for some compartments within crop groups. Transfer factors were also calculated per soil group, as defined by their texture and organic matter content (Sand, Loam, Clay and Organic), and evaluation of transfer factors' dependency on specific soil characteristics was performed following regression analysis. The derived estimates were compared with estimates currently in use.

Experimental study on in vitro tumor cell killing by focused bi-frequency ultrasound activated hematoporphyrin derivatives

OBJECTIVE

As ultrasound has become an important therapeutic technique on tumor, in order to find the cell-killing effect of focused bi-frequency ultrasound activated hematoporphyrin derivatives, experimental study was processed in vitro.

METHODS

Tumor cells K562 and SW-480 were killed by focused bi-frequency ultrasound activated hematoporphyrin (Hp) derivatives under optimized ultrasonic parameters and the cell-killing effect was tested by MTT (Thiazolyl blue: 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) technique.

RESULTS

The lower frequency (0.6 MHz) was better than the higher (1.1 MHz) in activating hematoporphyrin derivatives; the bi-frequency was better than mono-frequency, and the cell-killing efficiency was 2-3 times of sum of the two kinds of ultrasounds which constitute bi-frequency. Incubation for the 16 h was better than 4 h after the cells exposed to the ultrasound.

CONCLUSION

The method of killing tumor cells by focused bi-frequency ultrasound activated hematoporphyrin derivatives is presented and evaluated in this paper.

[Differentiation of Ziyi Bencao as an apocrypha]

It is generally believed that Ziyi Bencao is a book of the pre-Qin period. By studies on several aspects, including ancient bibliographical records, relics unearthed in Mawangdui Han tombs, nomenclature of ancient book titles, the date of appearance of ancient classics, contradictions between the time of activities of Bian Que and Ziyi, it is concluded that, in the pre-Qin period, there were no classic of herbology of any kind, even less Ziyi Bencao. The books entitled Ziyi Bencao recorded in bibliographies after Han Dynasty are all apocryphas made by Han authors.

[Differential analyses on the historical relationship between Zhenglei bencao (herbology of classified syndromes) and Mingyi Bie Lu (appendant records of famous physicians)]

This author claims that, by using the approach of "inclusion of all canons", Tao Hongjing incorporated the 365 kinds of drugs from the earliest canon "Shen Nong's Herbological Canon" with another 365 kinds of "subordinated drugs from famous physicians", including Wu Pu and Li Dangzhi etc. to compile his 7-volume "Collected variorum of herbological canon". Owing to the changes and modifications made on the term "subordinated drugs from famous physicians" by the prefaces of herbological works of successive ages, the misunderstandings that the other 365 appendant kinds of drug were derived from an available Ming Yi Bie Lu and that the preface by Tao Yinju of the Liang Dynasty in Zhenglei Bencao was the preface of the book Mingyi Bielu were thuw formed.

[Ultrasonic measurement of the elastic properties of goat condyles]

OBJECTIVE

The purpose of this experiment is to investigate the elastic properties of goat mandibular condyles and to provide basic constants for biomechanical study of temporomandibular joint.

METHODS

A fresh goat mandible was adopted and the standard condyle specimen of 4 mm x 6 mm x 10 mm was obtained from it. The structure density of the condyle was determined according to Archimede's principle. The transmitting velocities of ultrasonic wave in different directions of goat condyles were measured by using the ultrasonic system, which was composed of a transmitting transducer of 1.25 MHz, a receiving transducer of 2.5 MHz, an ultrasonic analyzer (5052UA) and a digital storage oscilloscope (HP54601A). The elastic coefficients and technical constants could be calculated by elastic equations.

RESULTS

The structural density of the sample and the wave velocities in different directions of the condyle were both obtained by direct measurement. And then, nine elastic coefficients and all of the technical constants of orthotropic condyles were calculated.

CONCLUSION

1. It is practicable to measure elastic properties of the condyle by using ultrasonic technique. 2. Goat condyles of the mandible are a type of anisotropic and linearly elastic material. 3. The direction perpendicular to the transverse ridge of the goat condyle has the highest Young's modulus. As to shear modulus, the direction along the transverse ridge shows the highest value.

On the direction and magnitude of radical substituent effects: the role of polar interaction on thermodynamic stabilities of benzylic C-H bonds and related carbon radicals

The C-H bond dissociation enthalpies (BDEs) of polarized benzylic molecules, i.e., para-substituted phenylacetonitriles (PANs), and the spin variations of the radicals of the general type p-GC6H4CH*-Y were investigated using density functional theory (DFT) calculations. In contrast to the commonly observed S-type substituent effect (see text), the present work shows that there should be three (rather than one) primary patterns (i.e., S, O, and counter-O) for remote G to affect spin and radical stability, depending upon the polarity of the alpha-Y group. Correlation analyses reveal that both the direction and magnitude of spin/radical effects are quantitatively related to the intensity of polar interaction in radical system, as registered by either the calculated group charges of the phenyl ring (C(Ph)) or by the polar constant sigma(+)s (Figures 1-4). A unified platform (Scheme 1) to rationalize the apparent differences of radical substituent effect is proposed.

A story: unpaired adenosine bases in ribosomal RNAs

In 1985 an analysis of the Escherichia coli 16 S rRNA covariation-based structure model revealed a strong bias for unpaired adenosines. The same analysis revealed that the majority of the G, C, and U bases were paired. These biases are (now) consistent with the high percentage of unpaired adenosine nucleotides in several structure motifs. An analysis of a larger set of bacterial comparative 16 S and 23 S rRNA structure models has substantiated this initial finding and revealed new biases in the distribution of adenosine nucleotides in loop regions. The majority of the adenosine nucleotides are unpaired, while the majority of the G, C, and U bases are paired in the covariation-based structure model. The unpaired adenosine nucleotides predominate in the middle and at the 3' end of loops, and are the second most frequent nucleotide type at the 5' end of loops (G is the most common nucleotide). There are additional biases for unpaired adenosine nucleotides at the 3' end of loops and adjacent to a G at the 5' end of the helix. The most prevalent consecutive nucleotides are GG, GA, AG, and AA. A total of 70 % of the GG sequences are within helices, while more than 70 % of the AA sequences are unpaired. Nearly 50 % of the GA sequences are unpaired, and approximately one-third of the AG sequences are within helices while another third are at the 3' loop.5' helix junction. Unpaired positions with an adenosine nucleotide in more than 50 % of the sequences at the 3' end of 16 S and 23 S rRNA loops were identified and arranged into the A-motif categories XAZ, AAZ, XAG, AAG, and AAG:U, where G or Z is paired, G:U is a base-pair, and X is not an A and Z is not a G in more than 50 % of the sequences. These sequence motifs were associated with several structural motifs, such as adenosine platforms, E and E-like loops, A:A and A:G pairings at the end of helices, G:A tandem base-pairs, GNRA tetraloop hairpins, and U-turns.

[Discussion on sources of texts of Meng Sheng's Herbology of dietotherapy cited in Jinling edition of Compendium of materia medica]

Most of the citations of Meng Sheng's Herbology of Dietotherapy in Compendium of Materia Medica are originated from the Daguan Herbology and Zhenghe Herbology. When comparing these sources of citations in Compendium of Materia Medica with the texts in Daguan and Zhenghe, it can be found that there are differences, In Compendium of Materia Medica, it is indicated that these sources marked "Meng Sheng's Herbology of Dietotherapy" are actually derived from other sources, while citations from other sources are marked "Meng Sheng's Herbology of Dietotherapy" which are not found in Classified Herbology (Zhenglei ben cao). This might be due to the editions of Daguan and Zhenghe Li Shizhen applied are different.

[Discassion on the date of appearance of the title Shen nong ben caojing (Shennong's Herbal Classic)]

It is said, in general literatures, that the title of shen nong ben cao jing appeared in pre- Qin period. It can be negated, through studies on Han shu yi wen zhi (Biblie - graphies in Book of Han Dynasty), relics unearthed from Han tombs in Mawangdui, the history of nomencleture for ancient books, and the date of appearance of ancient canons, that the said - title first appeared in the pre - Qin period. The name of "ben cao" was first appeared in western Han dynasty. There were officials of necromaneer (fan shi) and ben cao in western Han dynasty. During Chengdi Emperor of Han, some seventy such officials were dismissed and returned to their homelands. Pingdi Emperor re-summoned these officials. Several scores of officials responded to the edict, among them, those responsible for ben cao complied a book on ben cao (herbology) and alleged it to be written by shennong so as to win confidence with the authority and to acquire the official title of ben cao dai zhao (Herbal Attendant) for themselves. It is, therefore, natural that the title of shen nong ben cao jing can only have appeared at the time of Herbal Attendant in Western Han dynasty.

Study on the difference between Shennong's drug nature quoted by Wu Puu and by Shennong's drug in material medical in classified syndromes (Zheng)

Several questions were mentioned through the analysis and comparison of "Shennong's drug nature" (DN) as quoted by Wu Pu's Meteria Madica (WP) and Materia Medica of Classified Syndrome (Zheng) (ZL). These include: (1) The DN in ZL are incomplete, the "toxic nontoxic" terms were absent here; (2) There were different editions of ancient "Shennong's Canon of Materia Medica", carrying different numbers of drugs, including 365 kinds, 595, 441, 319 kinds respectively; (3) some of the drugs indicated as DN were, strangely, indicated as "drugs of supplemented Records" in ZL.

Removal of endotoxin from aqueous solutions by affinity membrane

Endotoxin was removed by affinity membranes with histidine immobilized as affinity ligand. Macropore cellulose membrane was prepared from filter paper by alkaline treatment and chemical crosslinking, and was used as matrix for the immobilization of affinity ligand. The matrix membrane was derived by hexamethylenediamine and activated by glutaraldehyde before histidine was immobilized. Membrane cartridges containing 40 or 80 sheets of affinity membrane were also prepared, which can be used to remove pyrogen from aqueous solutions. Using a cartridge with 40 sheets of affinity membrane, the endotoxin content in solution can be reduced to a minimum of 0.12 EU/mL.

Application of multiple-quantum line narrowing with simultaneous 1H and 13C constant-time scalar-coupling evolution in PFG-HACANH and PFG-HACA(CO)NH triple-resonance experiments

Many triple-resonance experiments make use of one-bond heteronuclear scalar couplings toestablish connectivities among backbone and/or side-chain nuclei. In medium-sized(15-30 kDa) proteins, short transverse relaxation times of Calpha single-quantum stateslimit signal-to-noise (S/N) ratios. These relaxation properties can be improved usingheteronuclear multiple-quantum coherences (HMQCs) instead of heteronuclear single-quantumcoherences (HSQCs) in the pulse sequence design. In slowly tumbling macromolecules, theseHMQCs can exhibit significantly better transverse relaxation properties than HSQCs.However, HMQC-type experiments also exhibit resonance splittings due to multiple two- andthree-bond homo- and heteronuclear scalar couplings. We describe here a family of pulsed-field gradient (PFG) HMQC-type triple-resonance experiments using simultaneous 1H and13C constant-time (CT) periods to eliminate the t1 dependence of these scalar couplingeffects. These simultaneous CT PFG-(HA)CANH and PFG-(HA)CA(CO)NH HMQC-typeexperiments exhibit sharper resonance line widths and often have better S/N ratios than thecorresponding HSQC-type experiments. Results on proteins ranging in size from 6 to 30 kDashow average methine CalphaH HMQC:HSQC enhancement factors of 1.10 +/- 0.15, withabout 40% of the cross peaks exhibiting better S/N ratios in the simultaneous CT-HMQCversions compared with the HSQC versions.

Phase labeling of C-H and C-C spin-system topologies: application in constant-time PFG-CBCA(CO)NH experiments for discriminating amino acid spin-system types

Triple-resonance experiments facilitate the determination of sequence-specific resonance assignments of medium-sized 13C,15N-enriched proteins. Some triple-resonance experiments can also be used to obtain information about amino acid spin-system topologies by proper delay tuning. The constant-time PFG-CBCA(CO)NH experiment allows discrimination between five different groups of amino acids by tuning (phase labeling) independently the delays for proton-carbon refocusing and carbon-carbon constant-time frequency labeling. The proton-carbon refocusing delay allows discrimination of spin-system topologies based on the number of protons attached to C alpha and C beta atoms (i.e. C-H phase labeling). In addition, tuning of the carbon-carbon constant-time frequency-labeling delay discriminates topologies based on the number of carbons directly coupled to C alpha and C beta atoms (i.e. C-C phase labeling). Classifying the spin systems into these five groups facilitates identification of amino acid types, making both manual and automated analysis of assignments easier. The use of this pair of optimally tuned PFG-CBCA(CO)NH experiments for distinguishing five spin-system topologies is demonstrated for the 124-residue bovine pancreatic ribonuclease A protein.

[Investigation on the various species of bulb of fritillary and its application]

Through studies on ancient herbological works, it is claimed that the fritillary recorded in the Classic of Poet, Shennong's Herbology is not identical with the fritillary applied today. It belongs to Balbostemma paiculatum (Maxim). Frang of Cucurbitacea. Ming Yi Bie Lu is the earliest book that includes the fritillary of Lilliae as a remedy, with its species Fritillaria thunbergii mig. It can be sure that this should include the latter species. The fritillaria of Sichuan makes its appearance in Ben Cao Hui Yan of the Ming dynasty. It is derived from F. unibracteata et K. C. Hsia and F. cirrkosa D. Don.

Design of a "minimAl" homeodomain: the N-terminal arm modulates DNA binding affinity and stabilizes homeodomain structure

This report investigates the sequence specificity requirements for homeodomain structure and DNA binding activity by the design and synthesis of a "minimAl" homeodomain (for minimalist design and alanine scanning mutagenesis) which contains the consensus residues and in which all nonconsensus residues have been replaced with alanine. The murine homeodomain Msx served as the prototype for the minimAl homeodomain, Ala-Msx. We show that Ala-Msx binds to DNA specifically, albeit with lower affinity than Msx. A derivative of the minimAl homeodomain, Ala-Msx(NT), which contains a native rather than an alanine-substituted N-terminal arm, has similar DNA binding affinity as Msx. We show that the native N-terminal arm stabilizes the tertiary structure of the minimAl homeodomain. Although Ala-Msx resembles a molten-globule protein, the structure of Ala-Msx(NT) is similar to Msx. The requirement for an intact N-terminal arm is not unique to the minimAl homeodomain, since the N-terminal arm also promotes high-affinity binding activity and appropriate tertiary structure of Msx. Therefore, the homeodomain "scaffold" consists of consensus residues, which are sufficient for DNA recognition, and nonconsensus residues in the N-terminal arm, which are required for optimal DNA binding affinity and appropriate tertiary structure. MinimAl design provides a powerful strategy to probe homeodomain structure and function. This approach should be of general utility to study the sequence specificity requirements for structure and function of other DNA-binding domains.

A new matrix for affinity chromatography and its application in the separation of a human monoclonal antibody

A method for the preparation of a p-aminobenzene sulphonyl ethyl containing crosslinked Sepharose 4B (ABSE-Sepharose 4B-CL) is described, trypsin, bovine serum albumin (BSA) and concanavalin A (Con A) were immobilized onto this matrix by diazotization. Conditions for the coupling reaction were investigated. The activity of immobilized trypsin reached 1.4 x 10(4) U/g, and 25 mg BSA can be coupled onto 1 g ABSE-Sepharose 4B-CL under the optimal conditions. An affinity medium with immobilized Con A as ligand was prepared by this method, and was used in the separation of a human monoclonal antibody.

DNA affinity cleaving analysis of homeodomain-DNA interaction: identification of homeodomain consensus sites in genomic DNA

We have incorporated the DNA-cleaving moiety o-phenanthroline-copper at amino acid 10 of the Msx-1 homeodomain, and we have analyzed site-specific DNA cleavage by the resulting Msx-1 derivative. We show that amino acid 10 of the Msx-1 homeodomain is close to the 5' end of the consensus DNA site 5'-(C/G)TAATTG-3' in the Msx-1-DNA complex. Our results indicate that the orientation of the Msx-1 homeodomain relative to DNA is analogous to the orientation of the engrailed and Antennapedia homeodomains. We show further that DNA affinity cleaving permits identification of consensus DNA sites for Msx-1 in kilobase DNA substrates. The specificity of the approach enabled us to identify an Msx-1 consensus DNA site within the transcriptional control region of the developmental regulatory gene Wnt-1. We propose that incorporation of o-phenanthroline-copper at amino acid 10 of a homeodomain may provide a generalizable strategy to determine the orientation of a homeodomain relative to DNA and to identify homeodomain consensus DNA sites in genomic DNA.

Membrane affinity chromatography used for the separation of trypsin inhibitor

Polysulphone (PS) was chemically modified by acrylation-amination and by chloromethylation-amination, respectively. An ultrafiltration membrane of chemically modified polysulphone (CMPS) was prepared by the phase inversion method. Trypsin was then covalently bonded onto the CMPS membrane by diazotization. The activity of immobilized trypsin reaches up to 10200 U/g; 15 mg trypsin was immobilized on 1 g CMPS membrane. Separation of soybean trypsin inhibitor was carried out on the affinity membrane, yielding 6.5 mg pure trypsin inhibitor in one run. The enzyme membrane has good activity and stability.

Zinc release from Xenopus transcription factor IIIA induced by chemical modifications

Xenopus transcription factor IIIA (TFIIIA) contains two tightly bound intrinsic Zn2+ ions that are released through treatment with either p-(hydroxymercuri)benzenesulfonate (PMPS) or diethyl pyrocarbonate (DEP) as monitored by the metallochromic indicator 4-(2-pyridylazo)resorcinol (PAR). The inactivation of TFIIIA by DEP as detected by an in vitro 5S RNA gene transcription assay was correlated with the extent of modification of histidine residues and Zn2+ release. Following reaction with PMPS, the 7S particle was dissociated into free TFIIIA and 5S RNA. This dissociation could be correlated with the extent of modification of cysteine residues as well as the Zn2+ release. The dissociation of the 7S particle was reversed by the addition of excess thiol reagent. However, the reversibility could be inhibited by EDTA, suggesting that Zn2+ was required for the binding of TFIIIA to 5S RNA. In the presence of PMPS- or DEP-modified TFIIIA or Zn2+-depleted TFIIIA, the fluorescence emission maximum of the hydrophobic probe, 8-anilinonaphthalenesulfonate, was blue-shifted by 30 nm, while only less than a 10-nm blue shift was observed in the presence of either the 7S particle or TFIIIA. These results indicate that the two Zn2+ ions in TFIIIA are coordinated with the cysteine and histidine residues and are required for maintenance of the proper conformation of TFIIIA.