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PubMed1987

Thermal stability of myosin rod from various species.

The radius of gyration and fraction helix as a function of temperature have been determined for myosin rod from four different species: rabbit, frog, scallop, and antarctic fish. Measurements from sodium dodecyl sulfate gel electrophoresis indicate that all particles have the same molecular weight (approximately 130K). All fragments are nearly 100% alpha-helical at low temperatures (0-5 degrees C). The melting profiles for each are qualitatively similar in shape, but their midpoints are shifted along the temperature axis in the following order: antarctic fish (Tm = 33 degrees C), scallop (Tm = 39 degrees C), frog (Tm = 45 degrees C), and rabbit (Tm = 49 degrees C). Corresponding radius of gyration vs temperature profiles for each species are shifted to lower temperatures (approximately 5-8 degrees C) with respect to the optical rotation melting curves. From plots of radius of gyration vs fraction helix, we find a marked drop in the radius of gyration (from 43 to approximately 34 nm) with less than a 5% decrease in fraction helix for rabbit, frog, and antarctic fish rods, whereas the radius of gyration of scallop rod never exceeds 34 nm. Results indicate hinging of the myosin rod of each species. The thermal stabilities of the myosin rods shift in parallel with the working temperature of their respective muscles.

Animals↗
PubMed2001

Synthesis and identification in bacterial lipopolysaccharides of 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto- and -D-glycero-D-talo-non-2-ulosonic acids.

5,7-Diacetamido-3,5,7,9-tetradeoxy-D-glycero-D-galacto- and -D-glycero-D-talo-non-2-ulosonic acids were synthesized by condensation of 2,4-diacetamido-2,4,6-trideoxy-D-mannose with oxalacetic acid. Comparison of the 1H and 13C NMR data and the specific optical rotation values of these monosaccharides and the corresponding L-glycero-D-galacto and L-glycero-D-talo isomers synthesized earlier [Tsvetkov, Y. E.; Shashkov, A. S.; Knirel, Y. A.; Backinowsky, L. V.; Zähringer, U. Mendeleev Commun. 2000, 90-92] with data of the natural compounds enabled the identification in bacterial lipopolysaccharides of derivatives of 5,7-diamino-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic (legionaminic) acid and epimers of legionaminic acid at C-4 and C-8.

Legionella pneumophila↗
PubMed1971

The effects of glycols on the renaturation of soluble collagen.

The effects of a number of related glycols and substituted glycols on the renaturation kinetics of acid-soluble calf-skin collagen have been investigated. Optical rotation recovery was monitored at a fixed temperature in the presence of perturbants and the initial rates of reaction were determined. The effects of perturbants on stability of the native protein are compared with their action in the renaturing systems. The relationship between initial recovery rates and fixed-time [alpha]-values is shown to be dependent upon the renaturation temperature. The influence of perturbant concentration on recovery rates is discussed in terms of present theories of the mechanism of collagen renaturation.

Animals↗
PubMed1975

Evidence for the existence of a low spin complex in acidic methemoglobin: its structure and formation.

By means of electron spin resonance and magneto-optical rotation, specific low spin complexes in acidic methemoglobin are obtained. The formation of these complexes is explained by a specific stereochemical arrangement of the distal histidine in the absence of allosteric effectors inducing the formation of a low spin ligand at room temperature. At low temperature, however, the distal histidine is directly bound to the heme iron. As the formation of the low spin complexes depends on allosteric effectors it is suggested that via the distal histidine the affinity of heme iron ligands is modified.

Allosteric Site↗
PubMed1976

On the sol-gel transition insolutions of kappa-carrageenan.

The disorder-order transition, which takes place at the gelpoint of k-carrageenan solutions was monitored by optical rotation and light scattering measurements. The coincidence of both sets of experimental data affords good evidence that the sol-gel transition is accompaned by a conformational change. Transition temperatures were observed to be linearly dependent on the logarthm of the salt concentration and this result is explained by the formation of double helices. Heats of gelation were measured by differential scanning calorimetry. It was found that the enthalpy increases with ionic strength, which was ascribed to the occurrence of a secondary process in which double helices are assembled into larger aggregates.

Calorimetry↗
PubMed1995

Cyclic analogues of wasp kinins from Vespa analis and Vespa tropica.

Syntheses are described of two bradykinin-like kinins isolated from Vespa analis (G-R-P-P-G-F-S-P-F-R-V-I, VSK-A) and Vespa tropica (G-R-P-Hyp-G-F-S-P-F-R-V-V, VSK-T) and of their cyclic analogues. Linear dodecapeptides were prepared by the solid-phase procedure based on Fmoc-chemistry, and cyclization was carried out by the diphenyl-phosphorylazide method. Peptide were characterized by amino acid analysis, optical rotation, analytical HPLC and FAB-MS. The conformational features of the cyclic and linear kinins were determined by circular dichroism measurements in water, 95% trifluoroethanol and 8 M guanidinium chloride. Consistent with previous findings, preliminary pharmacological experiments on smooth muscle preparations showed that cyclic wasp kinins were 50-100 times less potent than their linear analogues. Moreover, cyclo-VSK-A and cyclo-VSK-T behave like kininase inhibitors by preventing the degradation of straight kinins.

Amino Acid Sequence↗
PubMed1975

The synthesis and chemical properties of polyisoprenyl beta-D-mannopyranosyl phosphates.

2,3,4,6-Tetra-O-acetyl-beta-D-mannopyranosyl phosphate, free of the alpha anomer, was coupled with citronellol and dolichol in the presence of triisopropylbenzenesulfonyl chloride to give, after chromatographic purification and deacetylation, the respective polyisoprenyl beta-D-mannopyranosyl phosphates. These compounds were compared with the previously synthesized alpha anomers by means of their chromatographic properties, spectra, optical rotations, and hydrolysis reactions when treated with acid and alkali. To characterize the compounds resulting from these treatments, and to determine the mechanism of the alkaline hydrolysis, beta-D-mannopyranosyl phosphate was converted into beta-D-mannonpyranose 1,2-phosphate, and hence into D-mannose 2-phosphate, obtained as a mixture of alpha and beta anomers, characterized by infrared and nuclear magnetic resonance spectra and elemental analysis. Beta-D-Mannopyranosyl phosphate was readily separated by thin layer chromatography from the corresponding alpha anomer.

Chromatography, Thin Layer↗
PubMedDate not supplied

[Characteristics of isoelectric fractions of human serum albumin].

Amino acidic composition, dispersion of optic rotation, differential temperature-perturbation spectra, molecular weight and terminal amino acids are studied for certain isoelectric fractions of human serum albumin obtained by means of isoelectric focusing in the borate-polyol system. The isolated three isoelectric fractions with pI 4.7, 4.9 and 5.1 revealed no significant differences in the composition of amino acids. They also did not differ in molecular weight and N- and C-terminal amino acids. However certain differences in the conformation and number of perturbed thyrosils are detected by means of spectral methods.

Amino Acids↗
PubMed1999

Comparison of three optical methods to study erythrocyte aggregation.

The aim of this work was to evaluate three optical methods designed to determine erythrocyte aggregation: Erythroaggregometer (EA; Regulest, France), Laser-assisted Optical Rotational Cell Analyzer (LORCA; Mechatronics, Netherlands) and Fully Automatic Erythrocyte Aggregometer (FAEA; Myrenne, GmbH, Germany). Blood samples were taken from fifty donors (26 males and 24 females). The aggregation of normal red blood cell (RBC) and RBCs suspended in three normo- and hyperaggregating suspending media was studied. The results revealed some significant correlations between parameters measured by these instruments, in particular, between the indexes of aggregation of EA and LORCA. Further, RBC aggregation of multiple myeloma patients was also studied and a hyper erythrocyte aggregation state was found by EA and LORCA.

Adult↗
PubMed2005

Crystal structure of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside. Stabilization of the crystal lattice by a double network of N-H...O, O-H...N and O-H...O interactions.

The structure, conformation and configuration of methyl 3-amino-2,3-dideoxy-beta-D-arabino-hexopyranoside were investigated by (1)H NMR, (13)C NMR and IR spectroscopy, as well as by optical rotation. The crystal structure was confirmed by single-crystal X-ray crystallographic analysis at 293 K and R = 0.0434 based on 910 independent reflections. The crystal belongs to the monoclinic system, space group of P2(1) with cell dimensions a = 6.050(1) Angstroms, b = 7.284(1) Angstroms, c = 10.289(2) Angstroms, beta = 104.69(3) degrees, D(c) = 1.341 Mg cm(-3) and V = 438.9(1) Angstroms(3) for Z = 2. Furthermore, the molecule has a typical (4)C(1) chair conformation. Hydrogen bonds between sugar molecules are responsible for stabilizing the crystal lattice.

Carbohydrate Conformation↗
PubMed1990

Solvent effects on the cooperative order-disorder transition of aqueous solutions of schizophyllan, a triple-helical polysaccharide.

A triple helical polysaccharide schizophyllan in aqueous solution exhibited a highly cooperative transition between ordered and disordered states associated with the conformation of its side chains and nearby water molecules. The transition was followed by optical rotation and calorimetry using water containing additives such as NaOH and DMSO as solvents. The ordered state was stabilized or destabilized depending on the kind and amount of the additive employed; in particular, the addition of DMSO had a remarkable stabilizing effect. This effect was analyzed by means of a statistical mechanical theory of linear cooperative transitions, where DMSO was assumed to interact favorably with the ordered side chains. A small amount of NaOH in a solvent mixture stabilized the ordered state and made the transition curve very gradual. No molecular mechanism was elucidated to account for the role of NaOH.

Calorimetry↗
PubMed2001

Spectroscopic methods for determining enantiomeric purity and absolute configuration in chiral pharmaceutical molecules.

Analytical support, such as methods development, along with identification and characterization of intermediates and impurities, are critical in the development of a chemical process. The preparation of a drug substance requires the development of analytical methods for monitoring reactions and identifying impurities. Methods development for a chiral drug molecule is more difficult as the method must be capable of monitoring the overall reaction as well as possible racemization of starting materials and products. Chiral methods are often required to monitor the reaction steps of a synthesis, however, the development of enantiomeric purity methods are time-consuming and expensive. The use of chiroptical detectors, such as circular dichroism (CD), optical rotation (OR) and vibrational circular dichroism (VCD), can help to reduce or eliminate the need to develop chiral monitoring methods and also to predict absolute configuration. Recently, VCD has shown remarkable success with the latter and currently holds the most promise as a general, direct method that can be used as an alternative to X-ray crystallography. Each of the mentioned techniques can help analytical chemists to reduce the time associated with traditional enantiomeric purity methods development and to determine absolute configuration. This review will discuss the scope and limitations of these techniques for the rapid and routine determination of both enantiomeric excess and absolute configuration.

Chromatography, High Pressure Liquid↗
PubMed1997

Influence of thermal history on the stability of gelatin gels.

Gelatin gel properties have been studied using three techniques. Optical rotation measurements have shown that the lower the ageing temperature, the faster the helix content increases but the lower the helix stability. Rheological measurements show that a small increase in temperature leads to a melting of some junction zones followed by a build up of new ones. By ageing the gel at two successive temperatures one can show the existence of two populations of junction zones with different thermal stabilities. The same result is shown on melting thermograms obtained by differential scanning calorimetry. All these results are consistent with the hypothesis of the presence of junction zones of various lengths, the thermostability of which being proportional to their lengths.

Calorimetry, Differential Scanning↗
PubMed1989

Structural studies on the fucosamine-containing O-specific polysaccharide of Proteus vulgaris O19.

The polysaccharide chain of Proteus vulgaris O19 lipopolysaccharide contains D-galactose, N-acetyl-D-glucosamine N-acetyl-D-galactosamine and N-acetyl-L-fucosamine in the ratio 1:1:1:1. The structure of the polysaccharide was established by full acid hydrolysis and methylation analysis, as well as by non-destructive methods, i.e. the computer-assisted evaluation of the 13C-NMR spectrum and computer-assisted evaluation of the specific optical rotation by Klyne's rule. The polysaccharide is regular and built up of tetrasaccharide repeating units of the following structure: ----3)-alpha-L-FucNAcp-(1----3)-beta-D-GlcNAcp-(1----3)-alph a-D-Galp- (1----4)-alpha-D-GalNAcp-(1---- The O19-antiserum cross-reacts with lipopolysaccharide from P. vulgaris O42, the structure of which is still unknown. No cross-reactions were observed with O-polysaccharides Pseudomonas aeruginosa O7 and Salmonella arizonae O59 in spite of some structural similarities.

Acetylgalactosamine↗
PubMed1985

Synthesis of thymosin alpha 1 by fragment condensation using tert.-butyl side chain protection.

A novel synthesis of thymosin alpha 1 by classical methods using seven tert.-butyl side chain protected fragments is described. Optimum conditions were found for the final DCC/HOBt coupling of the two key intermediates; decapeptide and octadecapeptide. Thymosin alpha 1 was purified by two stages of preparative HPLC (partial purification with C8 and final purification with C18 reverse phase silica gel) to give a 30% overall yield for the final four stages of synthesis (including catalytic hydrogenation of octadecapeptide, coupling, deprotection and purification). The product was shown to be homogeneous by thin-layer and paper high voltage electrophoresis, isoelectric focusing analysis, thin-layer chromatography and high performance liquid chromatography. Amino acid analysis, optical rotation, 1H-n.m.r. spectroscopy, FAB mass spectroscopy and peptide mapping after tryptic digestion confirmed the structure of thymosin alpha 1. Three minor stereoisomer contaminants were isolated by HPLC and characterized as [D-Lys14]-thymosin alpha 1, [D-Lys17]-thymosin alpha 1 and [D-Ala3]-thymosin alpha 1 resulting from racemization at Lys14, Lys17 and Ala3 during the coupling of the fragments. A final contaminant, isolated by HPLC, was characterized as N alpha-isobutyloxycarbonyl-thymosin alpha 1 (15-28), which results from "wrong way opening" of an activated mixed anhydride.

Amino Acid Sequence↗
PubMed2007

Spectroscopic rationalization of the separation abilities of decaproline chiral selector in dichloromethane-isopropanol solvent mixture.

A chiral column, with decaproline as the chiral selector, has broad chiral selectivity. To understand the separation mechanism of this chiral column, multiple spectroscopic techniques, including optical rotation, electronic circular dichroism, infrared absorption and vibrational circular dichroism, have been used here to study the conformation of the decaproline oligomer in isopropanol(IPA)/dichloromethane(DCM) mixtures. These studies indicate that decaproline oligomer adopts polyproline II conformation in IPA/DCM solvent system (0% IPA approximately 100% IPA). Hydrogen bonding interactions between C=O groups of decaproline and IPA molecules increase as the content of IPA in the solvent mixture increases up to 60% and become less significant from then onwards. These spectroscopic observations are found to have a good correlation with the enantiomeric separation of racemic 2,2,2-trifluoro-1-[10-(2,2,2-trifluoro-1-hydroxy-ethyl-anthracen-9-yl]-ethanol by the decaproline column.

2-Propanol↗
PubMed1976

Structural determination of three glycoasparagines isolated from the urine of a patient with aspartylglycosaminuria.

Three different glycoasparagines have been isolated from the urine of a patient with aspartylglycosaminuria and their structures determined using sugar, amino acid and methylation analysis, enzymic degradation and measurements of the optical rotations. The structures were 2-acetamido-1-N-(4'-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine (yield 135 mg/l) beta-D-galactopyranosyl-(1 leads to 4)-2-acetamido-1-N-(4'-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine (yield 35 mg/l), and alpha-D-mannopyranosyl-(1 leads to 6)-beta-D-mannopyranosyl-(1 leads to 4)-2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 leads to 4)-2-acetamido-1-N-(4'-L-aspartyl)-2-deoxy-beta-D-glucopyranosylamine (yield 30 mg/l). The first two compounds have previously been described, whereas the third compound is different from any of the glycoasparagines isolated before.

Acetylglucosamine↗
PubMed1994

Native ordered structure of welan polysaccharide: conformational transitions and gel formation in aqueous dimethyl sulphoxide.

Welan, in aqueous solution, has "weak gel" properties analogous to those of ordered xanthan but, unlike xanthan, shows no evidence of conformational change between 0 and 100 degrees C. When the polymer is dissolved in dimethyl sulphoxide (Me2SO) rather than in water, however, there is a massive decrease in viscosity and total loss of gel-like character. In mixtures of the two solvents, the change in rheology occurs over a narrow range of composition (approximately 85-90% v/v Me2SO for 0.5% welan). On heating and cooling in a solvent close to the lower end of the critical range (86% Me2SO), the polymer shows typical order-disorder and disorder-order transitions [as monitored by optical rotation, differential scanning calorimetry, and temperature-course of rheological change]. When solutions of disordered welan in Me2SO are poured into excess water they form cohesive strings of gel. We interpret these results as showing that: (1) the stable conformation of welan in water is the double helix structure identified by X-ray fibre diffraction in the solid state; (2) in native welan, as biosynthesised, the strands are perfectly paired, and ordered along their full length; (3) on exposure to high concentrations of Me2SO, the native structure is dissociated into disordered coils; (4) rapid renaturation from the disordered state gives shorter helices, with exchange of partners to form a stable cross-linked network.

Carbohydrate Conformation↗