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Results for “Optical Rotatory Dispersion”

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At least 649 records · Page 36Linked to original sources
PubMed1977

Physicochemical properties of a lipase from Pseudomonas fluorescens.

The molecular weight of traicylglycerol lipase (EC 3.1.1.3) from Pseudomonas fluorescens is estimated to be approx. 33 000 by sodium dodecyl sulfate electrophoresis and Sephadex G-75 gel filtration. The lipase appears to be a single-chain protein and contains neither sugar nor lipid. The enzyme has a sedimentation coefficient (S20,w) of 3.06, an intrinsic viscosity of 3.0 g/ml and a partial specific volume of 0.730 g/ml, with an isoelectric point of pH 4.46. Amino acid analysis showed that the enzyme contained few sulfur-containing amino acid residues with no disulfide links. The N-terminal residue of the enzyme was found to be alanine and optical rotation dispersion analysis showed that about 20% of the enzyme structure was in a helicla configuration.

Amino Acids↗
PubMed1972

Photolysis accompanying peptide absorption in proteins. Electrophoresis and optical rotary dispersion studies.

Exposure of proteins and polypeptides to ultraviolet radiation below 240 nm produces peptide cleavage which may or may not be accompanied by observable changes in conformation and optical rotary dispersion (ORD) properties, depending on the stability of the secondary and tertiary structure of the macromolecule under the experimental conditions. Helical and coiled forms of poly-L-glutamic acid undergo degradation at similar rates but only the helical form shows a significant change in rotatory properties. The helical form of poly-L-lysine, but neither the coiled nor beta forms, shows a change in [alpha](233) on irradiation at 233 nm. beta-Lactoglobulin shows essentially no change in [alpha](233) on irradiation in either dilute salt solution or 4 M urea at room temperature; however, in 4 M urea at 56 degrees C a large change occurs. A model is developed which shows that studies of the effect of radiation on ORD properties may be useful in providing information on possible intermediate steps in protein denaturation. The method is illustrated with results on bovine plasma albumin. A quantum yield, 4.3 x 10(-3) moles/einstein, was obtained for peptide cleavage in this protein at 225 nm. These studies, based on gel electrophoresis, also showed that the fragments produced are essentially random, suggesting that transfer of energy from aromatic residues is not an important contributor to the peptide photolysis. Possible errors which could arise in ORD and other studies involving intense ultraviolet radiation are considered.

Animals↗
PubMed1970

Sulfate-binding protein from Salmonella typhimurium: physical properties.

This protein binds sulfate strongly and is implicated in sulfate transport in Salmonella typhimurium. It has a molecular weight of 32,000 and an axial ratio of 4:1. Crystals are elongate prisms up to 0.5 millimeter. X-ray diffraction photographs give discrete crystalline reflections to a spacing of at least 2 angstroms. The unit cell is orthorhombic P2(1)2(1)2(1), with four molecules per unit cell of 40.8 by 47.5 by 136 angstroms. This is consistent with a highly asymmetric molecule such as the prolate ellipsoid suggested by the other physical measurements. Addition of sulfate had minimum effects on the physical properties as measured by light absorption, optical rotary dispersion, circular dichroism, fluorescence and its depolarization, nuclear magnetic resonance, and sedimentation velocity.

Bacterial Proteins↗
PubMed1998

Investigation of dispersion effects in ocular media by multiple wavelength partial coherence interferometry.

We report on quantitative measurements of group refractive indices and group dispersion in water and in human ocular media such as the cornea, the aqueous humor, the lens, artificial intraocular lenses, as well as a total value averaged over the media along the axial eye length of normal subjects and pseudophakic patients in vivo using dual beam partial coherence interferometry. Different optical thickness values due to the dispersion of the cornea are demonstrated using two spectrally displaced light sources. The displacement can be used to indirectly calculate the group dispersion of the human cornea in the spectral region between 810 nm and 860 nm. If the object under investigation is dispersive, resolution is limited due to a broadening of the detected signals. This broadening increases with group dispersion, i.e., the extent to which the group refractive index of the medium varies with wavelength and thickness of the tissue under investigation as well as with the spectral bandwidth of the light source. Measurements of the group dispersion in the cornea, lens and vitreous of pseudophakic and normal human eyes, show that the cornea and the lens are more dispersive than water-by a factor of about 5 and 2, respectively-in the investigated spectral region. The cornea is approximately threefold more dispersive than the human crystalline lens, the aqueous humor is less dispersive than water and the group dispersion of all ocular components together, averaged over the axial length of normal and pseudophakic eyes, was only slightly higher compared to that of water. Since the highly dispersive cornea and lens together have only a thickness of about one sixth of that of the axial eye length, it seems that their contribution to the group dispersive effect along the whole axial eye length is only small.

Aqueous Humor↗
PubMed1996

[Evaluation ultraviolet radiation penetration into human skin. II. experimental studies].

Direct reflections of ultraviolet (UV) radiation (280-400 nm wavelength) from the human skin were characterised for different types of individuals. On the ground of this characteristics, the total UV reflection coefficient in this range was estimated. A new, noninvasive method for measuring a linear absorption and dispersion coefficient of UV radiation in skin layer was proposed. It is based on the measurement of radiant flux dispersed inside the skin cover during its radiation by a beam with a given profile. The dispersive flux is measured beyond the light zone. The absorption and dispersion coefficients can be calculated according to formulas developed previously and published in part I--"Theoretical analysis". Preliminary measurements of the above mentioned parameters were performed for different types of individuals.

Absorption↗
PubMedDate not supplied

[Properties of human serum albumin in ischemic heart disease].

Conformational changes in blood serum albumin under heart ischemia are found from the dispersion parameters of optical rotation and circular dichroism. It is also found that patients with myocardium infarction have a considerable amount of carbohydrate components in the modified albumin form.

Carbohydrates↗
PubMed1985

Effects of anesthetics and dichlorodifluoromethane on the activities of glyceraldehyde-phosphate dehydrogenase and pectin methylesterase.

Solutions of glucose-3-phosphate dehydrogenase (GPD) and pectin methylesterase (PME) were exposed to various anesthetics and dichlorodifluoromethane (F-12) to determine the abilities of these chemicals to inhibit enzyme activity. An aqueous solution of PME was exposed to saturation levels of the test chemicals for 30 min at 21 degrees. All test chemicals were inhibitory (measured after release of the test chemical) with propane being most inhibitory followed in order by F-12, cyclopropane, Ethrane (F2HCOF2CCHClF) and halothane (CF3CHClBr). GPD was exposed to various concentrations of F-12 and halothane for various times at 0 degrees and 33 degrees. Halothane at 33 degrees and a saturation concentration reduced the initial reaction velocity of GPD to zero after a 10-min exposure period. F-12 was somewhat less inhibitory than halothane, but inhibition in all instances was irreversible. Halothane was found to affect the circular dichroism and optical rotary dispersion spectra of GPD, with the magnitude of the changes generally increasing with treatment time. The observed changes were believed to arise from side-chain transitions of GPD.

Anesthetics↗
PubMed1979

Mechanism of uricase action.

Uricase (urate:oxygen oxidoreductase, EC 1.7.3.3) exposes a positional and steric specificity in the enzymic conversion of urate to allantoin. C-2 of urate was recovered as C-2 of allantoin. By the consecutive oxidation and hydrolysis reactions a levorotatory intermediate was formed, presumably (-)-2-oxo-4-hydroxy-4-carbohydroxy-5-ureido-imidazoline. The absorption and optical rotation dispersion spectra of the intermediate were established. In the presence of borate buffer, the intermediate was transformed to (+)-alloxanate. The decay of the former compound depends on general base and acid catalysis. RS-(+/-)-allantoin was formed by chemical decarboxylation and S-(+)-allantoin by enzymic decarboxylation.

Allantoin↗
PubMed1975

Hyaluronic acid salt--a mechanoelectrical transducer.

Hyaluronic acid transduces a very gentle pressure into an electrical potential. Such pressure, depending on its direction, changes the optical rotary dispersion properties of the salt, either increasing the rotation in the direction already shown by the unpressured salt or changing and increasing the rotation in the opposite direction. These finding have implications for understanding the function of the cochlear and vestibular fluids, renal function, and the approximation to frictionless motion of normal joints.

Chlorides↗
PubMed1982

[Use of the physicochemical characteristics of serum albumin for diagnosing ovarian and uterine cancer].

The frequency and causes of diagnostic errors are discussed on the basis of 2,099 case histories of ovarian and uterine tumors. The use of physico-chemical characteristics of serum albumin as an additional means of diagnosis of these diseases in 16 patients and 20 healthy subjects was studied. Patients revealed changes in dispersion of optical rotation of serum albumin which suggest its despiralization. Although being nonspecific, changes in the extent of despiralization vary depending on tumor advancement and gravity of patient's condition. The level of modified serum albumin is also in correlation with tumor process and the patient's state, the highest values being registered at later stages of the disease.

Chemical Phenomena↗