Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Optical Rotation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed2004

The chirality of dendrimer-based supramolecular complexes.

Boc-protected L-phenylalanine has been connected to a spacer-armed ureido-acetic acid derivative, which can form multiple supramolecular complexes with urea-adamantyl modified poly(propylene imine) dendrimers in chloroform. Complexes of this guest with several generations of urea-adamantyl dendrimers were prepared. The dendrimer-guest complexes were characterized in detail by (1)H-NMR, (1)H-(1)H-NOESY spectroscopy and mass spectrometry to prove their formation. Optical rotation experiments performed on different generations of dendrimer-guest complexes showed a constant positive value. These observations indicate that, though guest molecules decrease the flexibility at the periphery of the dendrimer upon binding, the amino acid at the terminus of the guest molecule retains its high local conformational freedom. This is in agreement with values found for covalently modified spacer-armed dendrimers.

Journal Article↗
PubMed1965

SEED POLYSACCHARIDES AND THEIR ROLE IN GERMINATION. A SURVEY OF THE POLYSACCHARIDE COMPONENTS OF MUSTARD SEEDS WITH SPECIAL REFERENCE TO THE EMBRYOS.

1. Methods were developed for the extraction, fractionation and purification of the more soluble polysaccharides of mustard-seed embryos. 2. One of these components was a pure homopolysaccharide, an araban, which was characterized by analysis, optical rotation, chromatography on diethylaminoethylcellulose and electrophoresis; the hydrolysis products of the methylated polysaccharide were isolated and characterized by the formation of crystalline derivatives. From these studies it emerges that mustard-seed araban is very similar to the family of pectic arabans, except that it is more highly branched than usual and contains a proportion of 1-->2-linkages. 3. A survey of the other polysaccharides of mustard seed, both in the embryos and in the seed coats, suggests a predominance of pectic-type polysaccharides.

Alkylation↗
PubMed1965

The effect of ultraviolet irradiation on soluble collagen.

1. The effect of ultraviolet irradiation on acid-soluble and neutral-salt-soluble calf-skin collagen was studied by chromatography, gel filtration, amino acid analysis and sedimentation of the sub-units, and the reaction kinetics of degradation were obtained from viscosity and optical rotation measurements. 2. It was demonstrated that, whereas the structure of neutral-salt-soluble calf-skin collagen may be represented by the formula (alpha(1))(2)alpha(2), the acid-soluble extract has the formula alpha(1).(alpha(2))(2). The acid-soluble collagen is also unusual in containing a large amount of a component that could be beta(22). 3. Ultraviolet irradiation causes the progressive degradation of the collagen molecule into smaller molecular fragments that subsequently lose their helical nature. The rate constants show that the denaturation of soluble collagens by ultraviolet irradiation is much slower, under the conditions used, than denaturation by heat or enzymes.

Journal Article↗
PubMed1967

Partial characterization of the sialic acid-free forms of alpha-1-acid glycoprotein from human plasma.

Some of the properties of sialic acid-free alpha(1)-acid glycoprotein prepared by mild acid hydrolysis (pH1.6 at 80 degrees for 1hr.) were compared with those of neuraminidasetreated alpha(1)-acid glycoprotein. Chemically, the former contained less fucose (15%) and amide (2%) residues. Physicochemically, it had undergone certain changes primarily pertaining to the secondary structure, so that the specific optical rotation was more negative than that of the latter. A further expression of this change is probably the difference in the pH range of the resolution into two bands on electrophoresis. The resolution of the glycoprotein prepared by mild acid hydrolysis seems to be extended to more acidic pH values both by starch-gel and free moving-boundary electrophoresis. On ultracentrifugation both preparations appeared homogeneous and sedimented with a rate of 3s. Removal of sialyl residues at different pH values, in the range 1-7, showed that 2moles of sialic acid/mole of protein are very strongly bound. The two variants of alpha(1)-acid glycoprotein were isolated from pooled sialic acid-free alpha(1)-acid glycoprotein by preparative starch-gel electrophoresis and from selected blood of normal adults by fractionation by solubility and chromatography. Ultracentrifugal and starch-gel electrophoretic analyses at pH5, with incubation times of 1 or 24hr., demonstrated that no dissociation-association equilibrium (constant sedimentation coefficient and molecular weight) or isomerization (constant apparent electrophoretic mobilities) exist between the two variants. Therefore these variants are not sub-units of native alpha(1)-acid glycoprotein but represent modifications of naturally occurring proteins. Further, it was shown that the difference in the electrophoretic mobilities between the two variants was not due to any difference in amide content. Immunochemically, the two variants share the same determinants.

Acids↗
PubMed1970

Invertebrate connective tissue. Isolation of D-arabinose from sponge acidic polysaccharide.

1. d-Arabinose, an extremely rare sugar in the animal kingdom, was isolated from a complex acidic polysaccharide obtained from the connective tissue of the sponge Hippospongia gossypina. A crystalline derivative of arabinose, the 1-benzyl-1-phenylhydrazone, was prepared and characterized by its melting point, optical rotation, and mixed melting point with authentic d- and l-enantiomers. 2. The distribution of arabinose within the animal kingdom is discussed, and a biological role is proposed for the spongonucleotides.

Animals↗
PubMed1986

Presence of fucosamine in teichuronic acid of the alkalophilic Bacillus strain C-125.

Cell walls of the alkalophilic Bacillus strain C-125 are composed of gamma-peptidoglycan, teichuronic acid and a polymer of glucuronate and glutamate. An amino sugar that was a main component of the teichuronic acid did not correspond to any of the commercially available hexosamines. The amino sugar was purified into crystalline form from the hydrolysate of the teichuronic acid by ion-exchange chromatography and then partition chromatography on a cellulose column. The amino sugar was identified as D-fucosamine (2-amino-2,6-dideoxy-D-galactose) by 400 MHz n.m.r. spectrometric analysis, measurement of optical rotation and elemental analysis.

Bacillus↗
PubMed2001

The effect of the transfusion of stored RBCs on intestinal microvascular oxygenation in the rat.

BACKGROUND: Although it is known that the transfusion of stored RBCs does not always improve tissue O(2) consumption under conditions of limited tissue oxygenation, the efficiency of O(2) delivery to the microcirculation by stored RBCs has never been determined. STUDY DESIGN AND METHODS: In a rat hemorrhagic shock model, the effects of resuscitation with fresh or 28-day-old RBCs stored in CPD plasma, saline-adenine-glucose-mannitol, and CPDA-1 plasma were investigated. Systemic hemodynamic and intestinal oxygenation measures were monitored. Intestinal microvascular PO(2) was determined with the O(2)-dependent quenching of palladium-porphyrin phosphorescence, and the RBC deformability was measured with a Laser-assisted optic rotational cell analyzer. RESULTS: Hemodynamic and oxygenation measures were significantly decreased during hemorrhagic shock. Intestinal oxygen consumption and mesenteric venous pO(2) were restored with the transfusion of both fresh and stored RBCs, except for CPD-stored RBCs. The intestinal microvascular pO(2) improved only with the transfusion of fresh RBCs. Deformability of the stored RBCs was significantly decreased. CONCLUSION: In contrast to that of fresh RBCs, the transfusion of stored RBCs did not restore the microcirculatory oxygenation, possibly because of impaired O(2) unloading, but, except for CPD-stored RBCs, the storage-induced changes were not enough to impair intestinal VO(2) and mesenteric venous pO(2).

Animals↗
PubMed2000

Three lycopodium alkaloid N-oxides from Huperzia serrata.

Three lycopodium alkaloid N-oxides, huperzine J (1), huperzine K (2) and huperzine L (3) were obtained from Huperzia serrata (Thunb.) Trev. Their structures were elucidated by spectroscopic methods and the relative configurations of 1 and 3 were established via NOESY NMR observations; optical rotation values and CD data are presented.

Magnetic Resonance Spectroscopy↗
PubMed2002

Ellagitannins from Lagerstroemia speciosa as activators of glucose transport in fat cells.

Glucose transport enhancers were searched for in Lagerstroemia speciosa, a Philippine local herbal medicine used for diabetes mellitus. Bioassay-guided fractionation of the aqueous acetone extract of the leaves afforded three active ellagitannins, lagerstroemin, flosin B and reginin A, identified by NMR and optical rotation. These compounds increased glucose uptake of rat adipocytes, and could be responsible for lowering the blood glucose level.

Adipocytes↗
PubMed2003

A new antioxidant isobenzofuranone derivative from the algicolous marine fungus Epicoccum sp.

The fungus Epicoccum sp., was isolated from the marine brown alga Fucus vesiculosus. After cultivation the fungus was investigated for its secondary metabolite content, and found to contain the new natural product 4,5,6-trihydroxy-7-methylphthalide (1, epicoccone), together with 5-(acetoxymethyl)-furan-2-carboxylic acid (2), furan-2-carboxylic acid (3), 5-(hydroxymethyl)-furan-2-carboxylic acid (4), (-)-(3 R,4 S)-4-hydroxymellein (5), and (-)-(3 R)-5-hydroxymellein (6). The structures of all compounds were determined by interpretation of their spectroscopic data (1D and 2D NMR, MS, UV, optical rotation and IR). Each isolate was tested for its antioxidative properties. Compound 1 was found to be potently active, showing 95 % DPPH radical scavenging effects at 25 microg/mL. Compound 1 also inhibited the peroxidation of linolenic acid in the TBARS assay (62 % inhibition at 37 microg/mL).

Antioxidants↗
PubMed2005

Calculation of Verdet constants with time-dependent density functional theory: implementation and results for small molecules.

We report the implementation of a method by which to calculate Verdet constants for molecules. The method is based on gauge-including atomic orbitals (GIAOs) and density functional theory. Calculations based on this method afford magneto-optical rotations of the right magnitude for the molecules H2, N2, CO, HF, CH4, C2H2, H2O, and CS2. The results are in satisfactory agreement with experiment. We investigate the dependency of the results on the gauge origin if GIAOs are not chosen, the convergence of the results with the size of the basis set for AOs and GIAOs, and for H2O and CS2 a comparison of gas-phase and liquid phase values. For the small molecules studied here, large polarized basis sets with diffuse functions are required to obtain well converged results. The use of an asymptotically correct Kohn-Sham potential is advantageous.

Journal Article↗
PubMed1976

Studies on the apoproteins of the major lipoprotein of the yolk of hen's eggs II. The dimer-tetramer transition of apovitellenin I.

Further studies have been made of the physical properties of hen's apovitellenin I, the principal low-molecular-weight protein from the high-lipid low density lipoprotein of the yolk of hen's eggs. The methods used included chromatography, sedimentation, viscosity, optical rotation, and spin labelling; the solvents used were aqueous urea, and, for some experiments, aqueous formamide. It is concluded that a neutral pH the protein is present in these solvents as an aggregate of molecular weight 36000 corresponding to a tetramer. Below about pH 4-5 solutions of the tetramer increased greatly in viscosity; furthermore, a covalently bound spin label increased in mobility. These changes were reversible and were apparently the result of dissociation of the tetramer to a dimer. This disociation did not involve a change in the proportion of alpha-helix. In contrast to the results of previous experiments, it now seems probably that the apovitellenin I dimer is stabilized by an interchain disulphide bond.

Animals↗
PubMed1973

Evidence for an amino-terminal extension in high-molecular-weight collagens from mature bovine skin.

Insoluble, mature collagen fibers from bovine skin have been partially solubilized by mild, denaturing, but nonhydrolytic means. The soluble denatured collagen was fractionated by alcohol coacervation, and a fraction rich in high-molecular-weight alpha-chains was obtained. The heavy alpha-chains were isolated by carboxymethylcellulose chromatography. Renaturation, followed by measurements of optical rotation at 365 nm, showed that stable, in-register renaturation was more readily accomplished in mixtures of heavy alpha-chains than in alpha1-beta(11)-chain mixtures. Renatured heavy alpha-chain preparations were precipitated in SLS form, negatively stained, and examined by electron microscopy. The SLS precipitates were compared with SLS segments from native soluble collagen and were found to match in band pattern and spacing along their entire length from the COOH-terminal region, except for an NH(2)-terminal extension of 170 +/- 30 A in the heavy alpha-chain SLS. The heavy alpha-chains correspond chromatographically with those previously reported to be intermediates in the conversion of procollagen to collagen, on the basis of their molecular weight and of labeling studies. The presence of NH(2)-terminal extensions, and their existence in mature insoluble collagen, suggest that these intermediates may have a special role in fibril formation.

Adenosine Triphosphate↗
PubMed1975

The structure and function of immunoglobulin domains: studies with beta-2-microglobulin on the role of the intrachain disulfide bond.

Beta-Microglobulin, a low-molecular-weight protein structurally related to the homology regions of immunoglobulins, has been used to study the role of the intrachain disulfide bond in the unfolding of immunoglobulin domains. The intact protein could be reversibly unfolded in guanidine hydrochloride, as judged by circular dichroism and optical rotation. Similarly, reoxidation of the reduced protein, during transfer from high concentrations of guanidine to neutral aqueous buffer, yielded a product with spectral characteristics typical of the native protein. However, if the free SH groups were prevented from reoxidizing either by chemical modification or by holding them in the reduced state, the molecule appeared to be in the randomly coiled state even under conditions where the intact protein is in the native conformation, judged on the basis of chiroptical measurements. The complement-fixing activity exhibited by native beta-2-microglobulin was retained by the reduced and alkylated derivative, suggesting that the site may be formed from a linear array of amino acids. We suggest a model for the folding of beta-2-microglobulin (and immunoglobulin domains) in which one of the early folding events results in disulfide bond formation, the latter being an obligatory step for continued folding to the native state.

Beta-Globulins↗