Implications of chemical and physical factors on the biological processing of lignocellulose

It is hoped that recognition of the chemical and physical factors touched on above will lead to their assimilation early in the process development. Although the depolymerization of plant cell wall material and the subsequent metabolism of the fragments are entirely effected by biological processes in nature, practical considerations of rates, concentrations, selectivity and susceptibility will require chemical or physical processing as well for the production of chemicals and materials from wood. These processes will break the polymers down into small molecules or at the very least serve as pretreatments to confer accessibility to the polymers in lignified cell walls. Further conversion of the small molecules into useful chemicals and materials may then be carried out by either biological or chemical processing as desired.     

Conformational changes in azurin from Pseudomona aeruginosa induced through chemical and physical protocols

Azurin from Pseudomona aeruginosa is a small copper protein with a single tryptophan (Trp) buried in the structure. The Gibbs free energies associated with the folding of holo azurin, calculated monitoring Trp fluorescence and changes in absorbance on the ligand-to-metal band, are different because these techniques probe their local environments, thereby being able to probe different conformational changes. The presence of an intermediate state was observed during the chemical denaturation of the protein. Upon denaturation, a 30-fold increase is observed in the magnitude of the quenching constant of the tryptophan fluorescence by acrylamide, because this residue becomes more accessible to the quencher. Entrapping the protein in sol-gel materials lowers its stability possibly because the solvation properties of the macromolecule are changed. The thermal denaturation of azurin immobilized in a sol-gel monolith is irreversible, which tends to rule out an aggregation mechanism to account for the irreversibility of the denaturation of the protein free in solution. Unlike the Cu(II) ion, the Gd(III) ion accommodates in site B of azurin with high affinity and the folding free energy of Gd-azurin is larger than that of apo azurin.     

Gamma-radiation induced ADP-ribosyl transferase activity and mammalian longevity

The levels of ADP-ribosyl transferase (ADPRT) activity following a standardized dose of 100 Gy gamma-radiation have been determined in leukocytes from 12 different mammalian species. Here, we report that the 100 Gy-induced levels of ADPRT correlated in a highly significant manner to the line spans of the mammals.     

黑莓汁的理化特性及贮藏期营养成分的变化

对黑莓浓缩汁的理化特性及其营养成分变化进行研究,结果表明：ｐＨ３～４,波长５１１～５１４ｎｍ时,果汁色泽最佳;果汁抗氧化还原能力很弱,但具有很强的光和热的稳定性。０～４℃低温贮藏１年后,６种维生素的损失率都超过５０％;含糖量损失４０７％;ＳＯＤ活性和氨基酸含量分别损失１０％和１２４％;含酸量略有增加     

Chondronectin: physical and chemical properties

Chondronectin, the chondrocyte attachment factor, was purified from chicken serum and characterized as to its physical and chemical properties. From sedimentation equilibrium data it was found to have a native molecular weight of 175,800 +/- 800 and a subunit molecular weight of 55,540 +/- 800 in the presence of guanidinium chloride and cysteine, suggesting a trimeric structure linked by disulfide bonds. As visualized by electron microscopy after rotary shadowing, the protein appears compact and globular. The amino acid and carbohydrate compositions of chondronectin are distinct from fibronectin, the fibroblast attachment factor, and laminin, the epithelial cell attachment factor. The activity of chondronectin in promoting attachment of chondrocytes is stable to digestion by collagenase, elastase, and neuraminidase, but is destroyed by trypsin treatment. The data suggest that chondronectin is structurally and chemically distinct from fibronectin and laminin.     

The physical and chemical properties of eumelanin

In this article, we review the current state of knowledge concerning the physical and chemical properties of the eumelanin pigment. We examine properties related to its photoprotective functionality, and draw the crucial link between fundamental molecular structure and observable macroscopic behaviour. Where necessary, we also briefly review certain aspects of the pheomelanin literature to draw relevant comparison. A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types. We are engaged in such an endeavor for the case of eumelanin.     

Age-related changes in chemical composition and physical properties of mucus glycoproteins from rat small intestine.

Mucus glycoproteins from newborn and adult rat small intestine were radiolabelled in vivo with Na2 35SO4 and isolated from mucosal homogenates by using Sepharose 4B column chromatography followed by CsCl-density-gradient centrifugation. Non-covalently bound proteins, lipids and nucleic acids were not detected in the purified glycoproteins. Amino acid, carbohydrate and sulphate compositions were similar to chemical compositions reported for other intestinal mucus glycoproteins, as were sedimentation properties. There were, however, important differences in the chemical and physical characteristics of the mucus glycoproteins from newborn and adult animals. The buoyant density in CsCl was higher for the glycoproteins from newborn rats (1.55 g/ml versus 1.47 g/ml). On sodium dodecyl sulphate/polyacrylamide/agarose-gel electrophoresis, the glycoprotein from newborn rats had a greater mobility than the adult-rat sample. Although both preparations had similar general amino acid compositions, variations were observed for individual amino acids. The total protein content was greater in the glycoprotein from newborn animals (27%, w/w, versus 18%, w/w). The molar ratio of carbohydrate to protein was less in the newborn, primarily owing to a decreased fucose and N-acetylgalactosamine content. Comparison of the molar ratio of fucose and sialic acid to galactose for both glycoproteins demonstrated a reciprocal relationship similar to that described by Dische [(1963) Ann. N.Y. Acad. Sci. 106, 259-270]. The sulphate content was greater in the glycoprotein from newborn rats (5.5%, w/w, versus 0.9%, w/w). Both had similar sedimentation coefficients in a dissociative solvent. These results suggest an age-related difference in the types of mucus glycoproteins synthesized by small intestine.     

Biological,physical and chemical changes in stored wheat

Six lots of wheat from six farmers' bins in Manitoba were adjusted to a range of 5 moisture contents, held at 6 temperatures and sampled at 6 times during storage. After sampling, seeds were surface sterilized with mercuric chloride and subsamples plated on Czapek's agar, on filter paper moistened with water, or on filter paper moistened with a 7.5% sodium chloride solution. The microflora on the seed was determined, germination counts were made, and the seed was examined by government inspectors for its condition and grade. A total of 1192 samples were examined. In addition, 180 samples were subjected to a fat acidity test. Deterioration for each combination of temperature and moisture, the fungi involved, and the consequent effect on condition, grade and fatty acid content were observed. The effect of high moisture content (>20%) and low temperatures (3–10 ° C) on infection of seed by Penicillium and the consequent effect on germination, condition, grade and fatty acid value are stressed. The interrelationship among fungi, and among fungi and temperature, moisture, storage time, fat acidity values and germination are indicated by correlation coefficient matrices.Deceased July 25, 1982.     

Structure of an apolipoprotein-phospholipid complex: apoC-III induced changes in the physical properties of dimyristoylphosphatidylcholine.

The effect of ApoC-III, a major apoprotein constituent of human very low density lipoproteins, on the physical properties of dimyristoylphosphatidylcholine (DMPC) vesicles has been studied by magnetic resonance and fluorescence techniques. The sharp gel-liquid crystalline transition usually observed at 23 C in DMPC is both broadened and elevated when ApoC-III is bound as determined (a) from measurements of microscopic viscosity by pyrene excimer fluorescence, (b) from the distribution of di-tert-butyl nitroxide between the bulk aqueous phase and the fluid lipid phase, and (c) from the motion of fatty acyl chains of spin-labeled phosphatdylcholine. Experiments involving the translocation of ascorbate and charged nitroxide ions and the movement of paramagnetic Eu 3+ ions indicate that when ApoC-III binds to DMPC vesicles, it increases their permeability or destroys their original bilayer structure. These two possibilities were distinguishable by gel filtration of the DMPC-ApoC-III complex (approximately 34 mol mol) that indicated that the product particles were significantly smaller than the original vesicles. Taken together, the data indicate that ApoC-III binding to DMPC not only decreases the acyl chain motion of individual lipid molecules, but also induces break-down of bilamellar vesicular structure to give significantly smaller complexes.     

Polyanion induced physical changes in isolated nuclei

Small angle light scattering techniques were used to determine the effects of selected polyanions on isolated mouse spleen nuclei. The light scattering measurements made it possible to distinguish nuclear swelling from lysis and/or aggregation. Heparin and dextran sulfate were shown to induce nuclear swelling. Chondroitin sulfate, although structurally similar to heparin, had no observable effect on the nuclei. Polystyrene sulfonate and pyran copolymer caused nuclear aggregation and lysis, respectively.