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1.
αD -N-acetyl neuraminic acid (Neu5Ac, sialic acid) is a commonly occurring carbohydrate residue in various cell surface glycolipids and glycoproteins. This residue is linked terminally or internally to Gal residues via an α(2 → 3) or α(2 → 6) linkage. In the cell surface receptor, sialyl-LewisX, a terminal α(2 → 3) linkage is present. Previous studies from our laboratory have shown that in solution LewisX adopts a relatively rigid structure. In order to model the Neu5Ac residue, vacuum molecular dynamics of this monosaccharide were compared with simulations that explicitly include solvent water. The dynamical average of the monosaccharide conformation obtained from the two simulations was similar. Vacuum calculations for the disaccharide Neu5Ac α(2 → 3) Gal β-O-methyl show that a number of low energy minima are accessible to this disaccharide. Molecular dynamics simulations starting from the low energy minima show conformational transitions with a time scale of 10–50 ps among several of the minima while large barriers between other minima prevent transitions on the time scale studied. Simulations of this disaccharide in the presence of solvent show fewer conformational transitions, illustrating a dampening effect of the solvent that has been observed in some other studies. Our results are most consistent with an equilibrium among multiple conformations for the Neu5Ac α(2 → 3) Gal β linkage. © 1994 John Wiley & Sons, Inc. 相似文献
2.
Srabani Bhaumik Jean Boyer Chaitali Banerjee Samantha Clark Noemi Sebastiao Elizabeth Vela Penny Towne 《Journal of cellular biochemistry》2020,121(12):4974-4990
In preclinical cancer studies, three-dimensional (3D) cell spheroids and aggregates are preferred over monolayer cell cultures due to their architectural and functional similarity to solid tumors. We performed a proof-of-concept study to generate physiologically relevant and predictive preclinical models using non–small cell lung adenocarcinoma, and colon and colorectal adenocarcinoma cell line-derived 3D spheroids and aggregates. Distinct panels were designed to determine the expression profiles of frequently studied biomarkers of the two cancer subtypes. The lung adenocarcinoma panel included ALK, EGFR, TTF-1, and CK7 biomarkers, and the colon and colorectal adenocarcinoma panel included BRAF V600E, MSH2, MSH6, and CK20. Recent advances in immunofluorescence (IF) multiplexing and imaging technology enable simultaneous detection and quantification of multiple biomarkers on a single slide. In this study, we performed IF staining of multiple biomarkers per section on formalin-fixed paraffin-embedded 3D spheroids and aggregates. We optimized protocol parameters for automated IF and demonstrated staining concordance with automated chromogenic immunohistochemistry performed with validated protocols. Next, post-acquisition spectral unmixing of the captured fluorescent signals were utilized to delineate four differently stained biomarkers within a single multiplex IF image, followed by automated quantification of the expressed markers. This workflow has the potential to be adapted to preclinical high-throughput screening and drug efficacy studies utilizing 3D spheroids from cancer cell lines and patient-derived organoids. The process allows for cost, time, and resource savings through concurrent staining of several biomarkers on a single slide, the ability to study the interactions of multiple expressed proteins within a single region of interest, and enable quantitative assessment of biomarkers in cancer cells. 相似文献
3.
Galectins show remarkable binding specificity towards beta-galactosides. A recently developed method for calculating binding free energies between a protein and its substrates has been used to evaluate the binding specificity of galectin-3. Five disaccharides and a tetrasaccharide were used as the substrates. The calculated binding free energies agree quite well with the experimental data and the ranking of binding affinities is well reproduced. For all the six protein-ligand complexes it was observed that electrostatic interactions oppose binding whereas the non-polar contributions drive complex formation. The observed binding specificity of galectin-3 for galactosides rather than glucosides is discussed in light of our results. 相似文献
4.
Anand C Umranikar C Shintre P Damle A Kale J Joshi J Watve M 《Journal of biosciences》2007,32(4):769-774
Many species of animal-pollinated flowers are known to vary widely in the nectar content of flowers. Some proportion of flowers
in many species is apparently nectarless, and such flowers are believed to be ‘cheaters’. Cheating may explain a part of the
variability in nectar content. If cheating exists as a qualitatively different strategy then we expect bimodality in the distribution
of nectar content of flowers. It has been shown in a multispecies study that gregarious species have a higher proportion of
cheater flowers. We studied the frequency distribution of total nectar sugar in two gregariously flowering species Lantana camara and Utricularia purpurascens, which differed in other floral and ecological characters. At the population level, both the species showed significant bimodality
in the total sugar content of flowers. The obvious sources of heterogeneity in the data did not explain bimodality. In Lantana camara, bimodality was observed within flowers of some of the individual plants sampled. In Utricularia purpurascens the proportion of nectarless flowers was more in high-density patches, suggesting that the gregariousness hypothesis may
work within a species as well. The results support the hypothesis of cheating as a distinct strategy since two distinct types
of flowers were observed in both the species. The effect of density in Utricularia purpurascens also supports the gregariousness hypothesis. 相似文献
5.
Riglar DT Richard D Wilson DW Boyle MJ Dekiwadia C Turnbull L Angrisano F Marapana DS Rogers KL Whitchurch CB Beeson JG Cowman AF Ralph SA Baum J 《Cell host & microbe》2011,9(1):9-20
Highlights? Merozoite attachment signals commitment to invasion and triggers subsequent events ? PfAMA1 and PfRON4 define core components of the merozoite-erythrocyte tight junction ? A ring of actin forms at the tight junction midway through merozoite invasion 相似文献
6.
In this work we examine the binding and folding of the membrane-active peptide, melittin in the presence of ganglioside GM1 micelle. The membrane bilayer is capable of inducing folding to small proteins and peptides upon binding. Using two-dimensional NMR techniques we have shown that at low concentration, GM1 micelle is able to induce an extended helical conformation to MLT. The pulsed-field gradient diffusion NMR study indicates that the peptide partition into GM1 micelle along with about 32% binding. While looking for the binding between MLT and GM1 using saturation transfer difference NMR spectroscopy, Val5, Leu9, Thr11, Ile17, Ser18, and Trp19 have been identified as the residues that are in close proximity to GM1 micelles. 相似文献
7.
A simple high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous determination of the pharmacologically important quinazoline alkaloids vasicine and vasicinone in Adhatoda vasica. The assay combines the separation and quantification of the analytes on silica gel 60 GF254 HPTLC plates with visualisation under UV and scanning at 270 and 281 nm. Using this technique, the alkaloidal content of different parts of the title plant have been determined. 相似文献
8.
Partitioning of small proteins and peptides from the aqueous to membrane phase is often coupled with folding. In this work we examine the binding and folding of the kinin peptide, bradykinin (BK), in the presence of the ganglioside monosialylated 1 (GM1) micelle. Using two-dimensional NMR techniques, we have shown that at low concentration, GM1 micelle is able to induce a turn conformation to BK. A pulsed-field gradient diffusion NMR study indicated that the peptide partitions into the GM1 micelle with a DeltaG(part) of -3.14 +/- 0.03 kcal/mol. A saturation transfer difference (STD) NMR study indicated that the binding is mostly through hydrophobic residues. 相似文献
9.
Chatterjee C Mukhopadhyay C 《Biochemical and biophysical research communications》2004,315(4):866-871
We report here the interaction of bradykinin with ganglioside GM1 by circular dichroism, steady-state fluorescence, and one-dimensional 1H NMR spectroscopy. Circular dichroism spectroscopy is indicative of a turn formation of bradykinin backbone in the presence of GM1 micelle. The fluorescence quenching efficiencies of iodide and acrylamide are substantially reduced, indicating a shielding of phenylalanine residue of bradykinin from aqueous environment. Significant line broadening of NMR resonances of bradykinin, suggestive of motional restriction, is observed. 相似文献
10.