Chemical and thermal cross-linking of collagen and elastin hydrolysates.

Chemical and thermal cross-linking of collagen soluble in acetic acid and elastin hydrolysates soluble in water have been studied. Solutions of collagen and elastin hydrolysates were treated using variable concentrations of 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Moreover, diepoxypropylether (DEPE) has been used as cross-linking agent. Films made of collagen and elastin hydrolysates were also treated with temperature at 60°C and 100°C to get additional cross-links. The effect of cross-linking has been studied using FTIR spectroscopy, thermal analysis, AFM and SEM microscopy. Mechanical and surface properties of materials have been studied after cross-linking. It was found that thermal and mechanical properties of collagen and elastin materials have been altered after thermal treatment and after the reactions with EDC/NHS and/or DEPE. Surface properties of collagen materials after chemical cross-linking have been modified. Thermal and chemical cross-linking of collagen films lead to alteration of polarity of the surface.

The use of blue-splashed white down in color sexing crosses.

Since the blue-splashed white (BSW) phenotype represents an alternative type of near-white down, a study was undertaken to see if it could be used in color sexing crosses as a background for the expression of sex-linked alleles at the silver (S, s+) and barring (B, b+) loci. The BSW is produced by homozygosity for the autosomal mutation, Bl, which results in blue plumage when heterozygous (Bl/bl+). The Bl/bl genotype reduces eumelanin in the down to a light grayish color. Also, like dominant white (I), it is relatively ineffective against pheomelanin. Silver (S) and gold (s+) were readily identifiable on BSW down in the presence of e+/e+ (wild type) and to a lesser degree with eb/eb (brown). Sexing was not possible using S and s+ with either E/-(extended black) or eWh/eWh (dominant wheaten). The addition of Co (columbian) enhanced the visual differentiation of silver and gold on all but the E/-background. As it does in the presence of dominant white, Co resulted in a marked increase in red pigmentation in subsequent plumages. The use of barring (B) was also an effective method for sexing chicks on a Bl/Bl E/-background. The presence of E was necessary to provide the even grayish down coloration in the head region for the expression of the B-induced head spot. the amount of red pigment in the broiler and adult plumage of the sex-linked offspring from this cross was further reduced by incorporating silver (S).

Exclusion of bacteriophage T1 by bacteriophage lambda. II. Synthesis of T1-specific macromolecules under N-mediated excluding conditions.

The results of experiments investigating T1 macromolecular synthesis under N-mediated excluding conditions failed to demonstrate a substantial alteration in the T1 mRNA production in excluding cultures at any stage in the T1 infectious cycle. The number of T1 DNA sequences in the excluding culture was found to be one-third to one-half that found in T1-infected cultures. The most severe reduction in T1-specific macromolecules was seen in protein synthesis. Total incorporation of labeled amino acids was reduced sixfold, and gel experiments confirmed that the T1-specific proteins capable of detection are reduced in excluding cells.

Exclusion of bacteriophage T1 by bacteriophage lambda. I. Early exclusion requires lambda N gene product and host factors involved in N gene expression.

Two modes of exclusion of T1 by lambda are distinguished. "Early" exclusion depends on gene N, but not on gene Q. It is at least partially ineffective against T1am23. "Late" exclusion depends on gene Q and effects T1am23 as well as T1+. Early exclusion is a direct effect of N gene product, rather than N gene being required for the expression of some other lambda gene. Three host mutations, groN, nusA, and nusB, known to interfere with lambda replication by affecting N gene expression, also interfere with the ability of lambda to exclude T1.