Physicochemical properties of succinylated calfskin pepsin-solubilized collagen

Some physicochemical properties of calfskin pepsin-solubilized collagen (PSC) and succinylated PSC (SPSC) were compared. The amino acid profile remained significantly unchanged. Sodium dodecylsulphate-polyacrylamide gel electrophoresis showed that subunits of SPSC migrated less than those of PSC. The denaturation temperatures of PSC and SPSC were 38.4 degrees C and 34.7 degrees C respectively. Succinylation slightly altered the triple-helical conformation of collagen, as determined by circular dichroism.     

Compliant film of regenerated Antheraea pernyi silk fibroin by chemical crosslinking

A compliant film was prepared by chemical crosslinking of fibroin from silk fiber of wild silkworm, Antheraea pernyi. The silk fiber was dissolved in concentrated aqueous lithium thiocyanate and desalinated by dialysis. The film was cast from the regenerated aqueous solution, and crosslinked by polyethylene glycol diglycidyl ether (PEG-DE). This film showed high water resistively while maintaining random coil and -helix structure, unlike films prepared by organic solvent treatment that causes β-sheet formation. The films containing about 20 wt.% crosslinker were remarkably compliant and tenacious. These features, combined with the living-cell affinity of the wild silkworm fibroin, are expected to be useful in biomedical applications.     

Improvement of the physical properties of reprocessed paper by using biological treatment with modified cellulase

A primary need for waste paper reprocessing is to preserve optical properties and the physical strength of the paper fibers. In this study, modified cellulase with copolymer, polyethylene oxide (PEO) derivatives and maleic anhydride (MA) was applied to the reprocessing of mixed office waste (MOW). Modified cellulase was prepared by a chemical reaction between amino groups of the cellulase and the MA functional groups of the copolymer. In MOW reprocessing, modified cellulase improved several physical properties of the paper including freeness, optical properties, and physical strength compared to the conventional process. Even though native cellulase improved the physical properties, paper treated with modified cellulase exhibited an increase in physical properties such as tensile strength and internal bond over those of unmodified cellulase. From these results, modified cellulase method is a new biological treatment that will save pulp resources, which are added to waste paper reprocessing to maintain the strength of paper.     

In-situ crosslinking of Aspergillus flavus lipase: Improvement of activity, stability and properties

Summary The mycelium-bound lipase of Aspergillus flavus was stabilised by cross-linkage using glutaraldehyde or methylglyoxal. Lipase activity was enhanced by up to 48% by treatment with methylglyoxal but not by glutaraldehyde. Cross-linking with methylglyoxal increased the thermal stability of the lipase by 58% at 50 °C     

Characterization of pepsin-solubilized bovine heart-valve collagen.

Collagens extracted from heart valves by using limited pepsin digestion were fractionated by differential salt precipitation. Collagen types were identified by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, amino acid analysis and cleavage with CNBr. Heart-valve collagen was heterogeneous in nature, consisting of a mixture of type-I and type-III collagens. The identity of type-III collagen was established on the basis of (a) insolubility in 1.7 M-NaC1 at neutral pH, (b) behaviour of this collagen fraction on gel electrophoresis under reducing and non-reducing conditions, (c) amino acid analysis showing a hydroxyproline/proline ratio greater than 1, and (d) profile of CNBr peptides on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis showing a peak characteristic for type-III collagen containing peptides alpha1(III)CB8 and alpha1(III)CB3. In addition to types-I and -III collagen, a collagen polypeptide not previously described in heart valves was identified. This polypeptide represented approx. 30% of the collagen fraction precipitated at 4.0 M-NaCl, it migrated between beta- and alpha1-collagen chains on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and its electrophoretic behaviour was not affected by disulphide-bond reduction. All collagen fractions from the heart valves contained increased amounts of hydroxylysine when compared with type-I and -III collagens from other tissues. The presence of beta- and gamma-chains and higher aggregates in pepsin-solubilized collagen indicated that these collagens were highly cross-linked and suggested that some of these cross-links involved the triple-helical regions of the molecule. It is likely that the higher hydroxylysine content of heart-valve collagen is responsible for the high degree of intermolecular cross-linking and may be the result of an adaptive mechanism for the specialized function of these tissues.     

Alteration of rheological properties of human erythrocytes by crosslinking of membrane proteins

The crosslinking of membrane proteins of human erythrocytes by diamide (diazene dicarboxylic acid bis(N,N-dimethylamide) ) was quantified by 4% polyacrylamide gel electrophoresis in 1% sodium dodecyl sulfate. The relation between the crosslinking of membrane proteins and erythrocyte functions (rheological and oxygen transporting) was quantitatively examined. (i) The crosslinking of membrane protein was induced by diamide, without changing the shape and the contents of intracellular organic phosphates (adenylates and 2,3-diphosphoglycerate). The intensity of spectrin 2 in SDS-polyacrylamide gel electrophoresis decreased proportionally to diamide concentration. The percentage decrease in spectrin 2 (using band 3 as an internal standard) was the most appropriate indicator for crosslinking ("% crosslinking'). (ii) The suspension viscosity of erythrocytes increased in proportion to the percentage of crosslinking, in the range of applied shear rates of 3.76-752 s-1. (iii) Erythrocyte deformability (measured by a high-shear rheoscope) was reduced by the crosslinking. The change was detectable even at 5% crosslinking. (iv) Rouleaux formation (measured by a television image analyzer combined with a low-shear rheoscope) was inhibited by the crosslinking. The inhibition was also sensitively detected at more than 5% crosslinking. (v) Hemoglobin in erythrocytes was chemically modified by higher dose of diamide (probably by the binding of diamide with sulfhydryl groups). Also the oxygen affinity of hemoglobin increased and the heme-heme interaction decreased. (vi) The reduction of the crosslinking of membrane proteins by dithiothreitol apparently reversed the intensity of spectrin bands in SDS-polyacrylamide gel electrophoresis and the erythrocyte functions (the suspension viscosity and the deformability), though not completely.     

The crosslinking and antimicrobial properties of tunichrome

Tunichromes are small peptides containing one or more dehydrodopa derived units that have been identified in the blood cells of at least eleven species of tunicates. Incubation of tunichromes isolated from Ascidia nigra hemocytes (or model dopa-containing compounds) under oxidative conditions with either lysozyme, cytochrome c or ovalbumin resulted in a time-dependent polymerization of these test proteins to dimers, trimers, tetramers and potentially to other oligomers. These results indicate that the oxidation products of tunichromes possess inherent crosslinking properties. Hence it is possible that tunichromes participate in tunic production by forming adducts and crosslinks with structural proteins and/or carbohydrate polymers, similar to the well-understood process of insect cuticle hardening. Since such crosslinking potentials could also be beneficial for defense reactions against invading microorganisms, antibacterial activity of tunichromes was tested using both a radial diffusion assay and the Microtox(R) test. Tunichromes exhibited antimicrobial activity against gram-negative bacteria Escherichia coli and Photobacterium phosphorium. However, they did not show any antimicrobial activity against the gram-positive bacteria Staphylococcus aureus at the concentrations tested. We propose that the crosslinking and antimicrobial functions are both based on the reactivity of dehydrodopa units present in the tunichromes, and their subsequent ability to form highly reactive quinone methides.     

Biocomposites of cellulose reinforced starch: improvement of properties by photo-induced crosslinking

In the present study, the composite films have been prepared from the aqueous dispersions of starch with microcrystalline cellulose using glycerol as plasticizer and irradiated under ultraviolet (UV) light using sodium benzoate as photo-sensitizer. Photo-crosslinking was characterized by measuring the water absorption under 100% relative humidity, swelling degree and gel fraction in dimethylsulphoxide (DMSO), upon irradiation time. Both, the incorporation of cellulose and photo-irradiation were found to decrease the water absorption, swelling in DMSO and increase the gel fraction. Thermal transitions indicated the anti-plasticization of amylopectin chains at the fiber/matrix interface. With increasing content of cellulose and photo-irradiation time, the tensile modulus and strength were found to improve. It is summarized that the combination of cellulose reinforcement and photo-crosslinking of matrix has improved the physical and mechanical properties.     

Improvement of degraded physical properties of a saline-sodic soil by reclamation with kallar grass (Leptochloa fusca)

A field experiment was conducted to evaluate the effectiveness of growing salt tolerant plants to improve the physical characteristics of a saline-sodic soil. Kallar grass [Leptochloa fusca (L.) Kunth], a species tolerant to salinity, sodicity and alkalinity, was irrigated for five years with poor quality ground water (EC = 0.14 S m^–1, SAR_adj=19.3, RSC = 9.7 meq L^–1). The soil physical properties of plant available water, saturated hydraulic conductivity, structural stability, bulk density and porosity were determined at the end of each year. The growth of kallar grass for three years significantly improved the physical properties of the soil and these were maintained with further growth of grass up to five years. Kallar grass significantly increased plant available water with time (r=0.97^**). The available water was highly correlated (r=0.92^**) with increases in soil organic matter content, porosity (r=0.99^**) and other physical properties. Soil hydraulic conductivity increased substantially with time from 0.035 to 55.6 mm d^–1 in the topsoil (0–20 cm) in five years and was significantly correlated with porosity, water retention, structural stability and organic matter content of soil. The soil structural stability index improved significantly from 32 to 151 with kallar grass and showed greater increases in the surface soil than at depth. The cropping of kallar grass resulted in a linear increase of soil organic matter content (r=0.92^**) which improved porosity and other soil physical properties (r0.82^*). This study confirmed that kallar grass is effective for rehabilitation and restoration of soil fertility in saline-sodic areas on a sustainable basis.     

Effects of anthocyanin-rich Kadsura coccinea extract on the physical,antioxidant, and pH-sensitive properties of biodegradable film

Food Biophysics - The pH-sensitive films were developed by adding Kadsura coccinea (KC) extract to chitosan (CH), gelatin (GL), and sodium alginate (SA) matrix. Due to abundant anthocyanin content,...     

Use of roentgen-television film for the analysis of physical exercises]

Biochemical investigation of movements of man is based on precise registration of movements of body links in space and time. The popular method of filming is almost unsuitable for studying exact movements in small joints, rotation movements and movements performed simultaneously in several joints. The use of rentgen-television filming of movement in the joints broadens the possibilities of biomechanical investigations of movements of man.     

生物被膜的物理特性及其表征

生物被膜涉及到人类生产生活的方方面面。生物被膜的形成有时是有益的,可用于生物降解、生物催化等;但同时也造成了诸多不利的影响,医疗领域中的感染性疾病、工业生产中的生物污损等均与生物被膜的形成有关。生物被膜形成过程中的物理性质决定着生物被膜的形态结构以及机械稳定性,对它在应对外界环境刺激并得以生存具有重要的意义。本文介绍了生物被膜形成初期和发展过程中的物理性质以及相应的表征手段。其中,细菌的表面粘附由细菌的近界面运动行为及细菌与表面的相互作用决定,并对生物被膜的初期形成起关键的作用。此外,机械性能测试发现成熟的生物被膜可看作具备粘弹性的聚合物。     

Improvement of oxidoreductase stability of cethyltrimethylammoniumbromide permeabilized cells ofZymomonas mobilis through glutaraldehyde crosslinking

Summary Permeabilization ofZymomonas mobilis with CTAB(Cetyltrimethylammoniumbromide) was investigated in order to obtain a stable process for sorbitol production in the immobilized system. The optimum conditions for sorbitol formation were treating cells with 0.2% CTAB at 4°C for 10 min. For the immobilized system permeabilized cells were treated with glutaraldehyde to improve the system with cross-linking of enzymes. In this way, no significant loss of enzyme activity was apparent during 30 day operation in a continuous process. The productivity of the continuous process at a dilution rate 0.2 h^–1 was 6.51g/L-h for sorbitol. The CTAB-permeabilized cells could be used to produce sorbitol and gluconic acid simultaneously in the long term continuous process.     

RNA-protein neighbourhoods of the ribosome obtained by crosslinking.

It is possible to crosslink protein to nucleic acid with diepoxybutane which reacts mainly with the N-7 of guanine as well as the thiol and aminogroups in protein; the resulting crosslinked complexes are cleavable. When this reagent is applied to ribosomes, even under conditions that minimize the extent of reaction, at least half of the ribosomal proteins can be recovered crosslinked to one or other of the major ribosomal RNA species. In addition, one fourth of the proteins can be recovered crosslinked to the RNA of the heterologous ribosomal subunit. Some of the remaining proteins may also be crosslinkable to the RNA, but additional experiments are required to confirm this.     

The immunomodulating properties of erythrocytes induced by physical factors]

It is shown that the action of ultraviolet rays (UVR) or magnetic field (MF) on the erythrocytes of intact Wistar rats by weight 140-170 g induces the property to stimulate the immune response on sheep's T-dependent antigen-erythrocytes and on bull serum albumin in allogenic transference. The most expressed immune stimulated effect is induced by the heavy erythrocytes, which are effected by magnetic field. The warming and vibration don't induce the immunomodulating characteristics in erythrocytes. By spleen cells sticking to glass, the modified UVR and MF, the heavy erythrocytes induce factors (differentiated in mass), which stimulate the development of immune response to T-dependent antigens of sheep's erythrocytes and of bull serum albumin. These factors depress the function of antigen-specific T-suppressors and induce the immune-suppressive characteristics in light erythrocytes.     

Effect of probucol on the physical properties of low-density lipoproteins oxidized by copper

Human plasma low-density lipoproteins (LDL) were incubated with 10 microM probucol for 1 h at 37 degrees C. Probucol incorporation into the LDL was complete as judged by filtration through a 0.2-micron filter, ultracentrifugation, and gel filtration. LDL with and without probucol were incubated for up to 24 h with 5 microM Cu2+ at 37 degrees C. Copper oxidation increased the content of random structure in the LDL protein from 30% to 36% at the expense of beta-structure (which decreased from 22% to 16%) without a change in alpha-helical content as measured by circular dichroism spectroscopy. This loss of beta-structure was prevented by the presence of probucol in the LDL during the copper incubation. Probucol reduced the rate of increase of fluorescence during copper oxidation at 37 degrees C. After 6 h, the fluorescence intensity at 360-nm excitation and 430-nm emission was 30% less in probucol-containing samples. Probucol had no effect on the circular dichroic spectrum of LDL and only minimal effects (less than 5%) on the fluorescence emission spectrum at wavelengths below 500 nm. Two fluorescence peaks, with emission at 420 nm and excitation at 340 and 360 nm, are resolved in three-dimensional fluorescence spectra of oxidized LDL. Probucol reduces the intensity of both peaks equally. The binding of a highly reactive heparin (HRH) fraction to LDL was measured by titration of LDL with HRH in the presence of fluoresceinamine-labeled HRH. The decrease in fluorescence anisotropy of the labeled HRH is proportional to the concentration of bound HRH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis and properties of a new cleavable nucleic acid-protein crosslinking reagent

A new compound, dithiobis[9-(2-ethylenecarbamoylethylamino)-2,3-dimethoxy-6-azido-acridine], was synthesized and used in some preliminary experiments to form cleavable complexes between nucleic acids and proteins. In a first step the azidoacridine moiety of the reagent intercalates between the bases of nucleic acids and is then bound by reaction of the azido group. The disulfide group of the reagent is simultaneously converted under reducing conditions into a thiol which, in a second step, can be bound by oxidation to -SH groups of a vicinal protein (additional -SH groups can be inserted in the protein using 2-iminothiolane). The nucleic acid-protein complexes thus formed can be redissociated by reduction. The potential applications of this new cleavable crosslinking reagent could be extended to topographical investigations of any biological structure composed of nucleic acids and proteins.