A transfection compound series based on a versatile Tris linkage.

The family of cationic lipid transfection reagents described here demonstrates a modular design that offers potential for the ready synthesis of a wide variety of molecular variants. The key feature of these new molecules is the use of Tris as a linker for joining the hydrophobic domain to a cationic head group. The molecular design offers the opportunity to conveniently synthesise compounds differing in charge, the number and nature of hydrophobic groups in the hydrophobic domain and the characteristics of the spacer between the cationic and hydrophobic moieties. We show that prototype reagents of this design can deliver reporter genes into cultured cells with efficiencies rivaling those of established cationic lipid transfection reagents. A feature of these reagents is that they are not dependent on formulation with a neutral lipid for activity.

A gentle method for linking Tris to amino acids and peptides.

A gentle method for the addition of Tris to the carboxyl group of amino acids or peptides for the purpose of altering their solubility and/or for providing sites for further derivatization is described. Under mild alkaline conditions and in high concentrations of aqueous dimethylformamide, the amino group of Tris cleaves simple esters of N-protected amino acids or peptides to form an amino acid-Tris linkage. The effects of pH, temperature and dimethylformamide concentration on the rate and the efficiency of the reaction of Tris with benzyloxycarbonyl-alanine methyl ester were examined and the general applicability of the method demonstrated on a range of amino acid and small peptide substrates. Side-chain protection was not required and the degree of racemization was found to be lower than with conventional chemical coupling.

Molecular species of epidermal growth factor carrying immunosuppressive activity.

The suppression of antibody formation to sheep red cells in mice by partially purified fractions of mouse submaxillary gland was shown to be caused by epidermal growth factor (EGF). Purification of EGF by the method of Savage and Cohen resolved three components referred to as EGF a, EGF b, and EGF c. All three induced premature eye opening in neonatal mice, but only EGF a (identified as EGF 1-53) had full immunosuppressive activity. EGF c was shown by micropeptide mapping of chymotryptic and thermolytic digests and amino-terminal analysis to differ from EGF a only by the presence of beta-aspartyl instead of an asparaginyl residue. EGF b differed from EGF a in that it lacked the N-terminal asparagine. EGF shortened enzymatically at its carboxy terminal by two or five amino acids did not have any immunosuppressive activity. These findings suggest that, in contrast to some other biological effects of EGF, intact amino and carboxy terminals are required for the expression of immunosuppressive activity.

Antigenic drift in the hemagglutinin of the Hong Kong influenza subtype: correlation of amino acid changes with alterations in viral antigenicity.

The nucleotide sequence of the gene coding for the large subunit of influenza virus hemagglutinin (HA1) was determined for strains A/NT/60/68, A/Eng/878/69, and A/Qu/7/70, three early isolates of the Hong Kong subtype. Sequences were obtained by the dideoxy chain termination method, using reverse transcriptase to synthesize partial DNA copies of the RNA gene. HA1 amino acid sequences predicted from the gene sequences were compared with published data for strains A/Aichi/2/68 and A/Vic/3/75. Compared with earlier strains, the HA1s of A/eng/878/69 and A/Qu/7/70 each contained three amino acid changes. Some of these were also found in A/Vic/3/75, but some were unique to the particular strain. When all of the strains were titrated with a panel of monoclonal antibodies directed against A/NT/60/68, alterations in viral antigenicity could be correlated with particular amino acid changes. The existence of multiple pathways for viral evolution during antigenic drift is discussed.

Extracellular polysaccharides of some basidiomycetes.

Culture filtrates of four basidiomycete fungi, Stereum strigoso-zonatum, Fomes australis, Trametes lilacinogilva and Polyporus tumulosus were fractionated and examined for polysaccharide content. Acid hydrolysis showed the presence of galactose, mannose, xylose, fucose and glucose. Their relative amounts were estimated by gas chromatography of the corresponding alditol acetates. Galactose and mannose were the major constituent sugars, amounting to more than 50% of the total. One of the polysaccharides, a fucogalactomannan elaborated by P. tumulosus, was isolated in a purified form. It was shown to have [alpha]D +42 degrees and contained galactose, mannose, fucose and xylose in the relative proportions 2 : 1 : 1 : 0-2.