Systematic variation in amino acid compositions of grass caryopses

Variation in amino acid patterns of 121 species (72 genera) of grass caryopses is extensively consistent with taxonomic groupings. The patterns of pooids and chloridoids are distinguishable from one another and from those of eu-panicoids and andropogonoids; the bamboos, Oryza, Stipeae, Ehrharta and Microlaena, which share certain morphological and anatomical features, also share a characteristic amino acid profile, while profiles of danthonoioids, Triodia and Aristida are clearly non-pooid. Caryopsis amino acid patterns vary independently of photosynthetic pathway. Embryos from taxonomically diverse genera all show very similar amino acid profiles, which differ strikingly from those of the endosperms, and the amino acid patterns of whole caryopses are dominated by their endosperms, which are responsible for the taxonomic variation. ‘Chemical scores’ of the caryopsis proteins, but not total protein contents, correlate to some extent with taxonomic groupings.     

Chemical modifications of actin: effects on interaction with deoxyribonuclease I

Maleylation of lysine residues, nitration of tyrosine residues or modification with 2,3-butanedione or 1,2-cyclohexanedione of arginine residues on actin resulted in a loss of polymerizability of the modified actin. However, only lysine modification produced a complete loss of the deoxyribunuclease I inhibitory ability of actin at low degrees of modification. By the level of one modified lysine per actin monomer, the samples completely lost polymerizability and lost 65% of their inhibitory power against deoxyribonuclease I-catalysed hydrolysis of DNA. By two lysines modified per actin, all inhibitory activity was lost. One lysine residue on actin apparently overlaps both an actin action contact site and an actin-deoxyribnuclease 1 contact site, offering a suggestion as to how deoxyribonuclease I blocks actin polymerization.     

Assignment of the gene for dipeptidase 2 to Mus musculus chromosome 18 by somatic cell hybridization

Evidence is presented for the assignment of the gene for dipeptidase 2 to Mus musculus chromosome 18 by synteny testing and karyotypic analysis of Chinese hamster × mouse somatic cell hybrid clones. DIP-2 and chromosome 18 were expressed concordantly in 24/24 clones examined (ten primary clones and 14 secondary clones). Synteny testing indicated that DIP-2 was not expressed concordantly with the expression of any marker enzymes.This work was supported by NIH grant USPHS GM 09966.     

The synthesis of 6-deoxy-6-fluoro-α,α-trehalose and related analogues

Selective acid-catalysed methanolysis of 2,3,2′,3′-tetra-O-benzyl-4,6:4′,6′-di-O-benzylidene-α,α-trehalose yielded the monobenzylidene derivative, which was converted into the 4,6-dimesylate. Selective nucleophilic displacement of the primary sulphonyloxy group then gave 2,3-di-O-benzyl-6-deoxy-6-fluoro-4-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-d-glucopyranoside. Removal of the protecting groups then yielded 6-deoxy-6-fluoro-α,α-trehalose. In addition, 6-deoxy-6-fluoro-4-O-mesyl-α,α-trehalose and a derivative of 4-chloro-4,6-dideoxy-6-fluoro-α-d-galactopyranosyl α-d-glucopyranoside were also prepared from the same substrate. Iodide displacement of 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranosyl 2,3-di-O-benzyl-4,6-di-O-mesyl-α-d-glucopyranoside afforded the 6-iodide and 6,6′-di-iodide in yields of 31 and 36%, respectively. Similarly, the 6-azide and 6,6′-diazide were isolated in yields of 17 and 21%, respectively.     

The reaction of phosphorus pentachloride with amides,in particular 2-acetamido-2-deoxyaldohexopyranoses

2-acetamido-2-deoxyaldohexopyranose polyacetates are transformed by the action of phosphorus pentachloride into 2-tetrachloroethylideneamino derivatives, the trans-2-acetamido-l-acetate system reacting more rapidly than the cis. A 1-acetamido-pyranosyl polyacetate afforded the 1-tetrachloroethylideneamino derivative and 2-O-trichloroacetyl-β-D-glucopyranosyl chloride. The latter was also observed, amongst other products, from the reaction of β-D-glucopyranosyl azide tetra-acetate with phosphorus pentachloride. Similar reactions on acetamidocyclohexane and its 2-acetoxy derivative afforded dichloroacetamido, trichloroacetamido, and tetrachloroethylideneamino derivatives. Likewise, 1-acetamido-2-acetoxyethane gave the 1-dichloroacetamido derivative.     

A comparison of the interfacial interactions of the apoprotein from high density lipoprotein and β-casein with phospholipids

The conformations adopted by β-casein and the total apoprotein from serum high density lipoprotein when spread at the air-water interface are compared; the monolayer data are consistent with the apoprotein being α-helical and the β-casein being disordered with segments distributed in loops and trains. The penetration of these hydrophobic proteins into phosphatidylcholine monolayers in different physical states was investigated. More protein can penetrate into monolayers when they are in the liquid-expanded state; for penetration at constant total surface area the lateral compressibility of the lipid is an important factor. The charge and conformation of the polar group of the phospholipid does not have a major influence on the interaction. The mixed films of lipid and protein have a mosaic structure; probably the β-casein is in a compressed state whereas the apoprotein is extended as α-helices in the plane of the interface. The chain-length dependences of the interaction of the apoprotein with phosphatidylcholine monolayers and bilayers are different; when the apoprotein binds to bilayers of shorter-chain phosphatidylcholines it alters the shape of the lipid-water interface whereas with monolayers the interface remains planar throughout.