Biomedical subjects

T Y Liu

Publications and source records attributed to T Y Liu.

At least 163 records · Page 9Linked to original sources

PubMed1977

Studies on Limulus amoebocyte lysate II. Purification of the coagulogen and the mechanism of clotting.

A coagulogen in Limulus lysate has been purified to apparent homogeneity as judged by sodium dodecyl sulfate-gel electrophoresis. The purified coagulogen identified by its ability to clot with either trypsin or the purified Limulus clotting enzyme (Tai, J.Y., and Liu, T. Y. (1976) Fed. Proc. 35, 1486) has a molecular weight of 24,500. It consists of a single polypeptide chain of about 220 amino acids with glycine and serine as its NH2- and COOH-terminal residues; respectively. When acted upon by the Limulus clotting enzyme, the coagulogen releases a soluble C-peptide of about 45 amino acids and an insoluble coagulin of about 170 amino acids. The latter interacts in a noncovalent fashion to form the clot. Amino acid analyses together with the results of NH2- and COOH-terminal analyses suggest that the clot formation involves the cleavage of an--Arg--Lys--bond. Trypsin acts on the coagulogen to cause clotting by splitting the same peptide bond.

Amino Acids↗

PubMed1977

Studies on Limulus amoebocyte lysate. Isolation of pro-clotting enzyme.

A pro-clotting enzyme capable of causing the gelation of clottable proteins in Limulus polyphemus (horseshoe crab) has been purified to apparent homogeneity as judged by sodium dodecyl sulfate-gel electrophoresis. The activation of the pro-clotting enzyme depended on the presence of both Ca+ and endotoxin. It contained gamma-carboxyglutamic acids and gave a single NH2-terminal lysine. The enzyme was inhibited by diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride, and soy bean trypsin inhibitor, indicating that it is a serine protease. The molecular weight of the proclotting enzyme was determined to be at least 150,000 by sodium dodecyl sulfate-gel electrophoresis under reducing and denaturing conditions. The protein appears to consist of a single peptide chain, since exposure of the reduced and carboxymethylated enzyme to 6 M guanidine hydrochloride failed to dissociate it into any subunits.

Amino Acids↗

PubMed1977

Primary structure of human C-reactive protein.

The complete amino acid sequence of human C-reactive protein has been established. Distant homologies to C3 homology region in the CH2 domain of IgG and to C3a anaphylotoxin have been noted. No homology to other immunoglobulin homology regions or to the same homology region in other heavy chains was observed. The previously reported homologies between rabbit and human C-reactive protein and protein C1t have been extended and strengthened.

Amino Acid Sequence↗

PubMed1977

Cross-antigenicity and immunogenicity between capsular polysaccharides of group C Neisseria meningitidis and of Escherichia coli K92.

Antibodies to capsular polysaccharides of group C Neisseria meningitidis are often found in sera of young adults despite infrequent nasopharyngeal carriage and low rate of attack of N. meningitidis in the United States. Thus, experiments were designed for detection of bacteria cross-reactive with N. meningitidis. Among 3,264 cultures of stool, urine, blood, and cerebrospinal fluid, only 14 strains were found to be cross-reactive; all were Escherichia coli possessing the K92 capsular polysaccharide. The somatic O-antigens were 16, 13, 23, and 73; the flagellar antigens were H4 and 34. All K92 strains of E. coli showed the expected fermentations, were sensitive to common antibiotics, and lacked enteropathogenicity. Antigens of both E. coli K92 and group C N. meningitidis are capsular, acidic polysaccharides composed of sialic acid. The K92 polysaccharide is N- but not O-acetylated, sensitive to neuraminidase, and linked by alpha-2,8- alternating with alpha-2,9-ketosidic bonds. The K92 polysaccharides from all E. coli studied had similar biophysical and immunological properties. Intravenous injection of formalin-treated K92 organisms induced precipitating and bactericidal antibodies to polysaccharides of N. meningitidis. E. coli K92 strains may provide an alternative immunogen for prophylaxis against disease due to group C N. meningitidis in infants and young children.

Adult↗

PubMed1977

Sialic acid-containing polysaccharides of Neisseria meningitidis and Escherichia coli strain Bos-12: structure and immunology.

A polysaccharide antigenically related to that of group C Neisseria meningitidis was isolated from Escherichia coli strain Bos-12 (O48: K91:NM). Like the polysaccharides of groups B and CN. meningitidis, the Bos-12 antigen was shown to be a pure polymer of sialic acid. The 13C-nuclear magnetic resonance studies of the groups B and C polysaccharides indicated that the former consists of units of sialic acid joined in alpha-2 leads to 8 linkages, whereas the latter contains sialic acid residues linked by alpha-2 leads to 9 glycosidic bonds. Chemical and nuclear magnetic resonance studies of the polysaccharide of E. coli strain Bos-12 established that it is a heteropolymer containing both alpha-2 leads to 8 and alpha-2 leads to 9 linkages. Physical parameters including partial specific volume, reduced viscosity, diffusion and sedimentation coefficients, shape, weight-average molecular weight, and the Stokes radius of the polysaccharides of groups A, B, and C N. meningitidis have been determined. The results indicate that the polysaccharides are highly asymmetric and exist in solution as rigid rods; aggregates are formed by the association of these rods. The polysaccharides appear to have "restricted" length.

Antibodies, Bacterial↗

PubMed1976

Primary structure of streptococcal proteinase. I Isolation, composition, and amino acid sequences of the tryptic and chymotryptic peptides of cyanogen bromide fragments 1 to 4.

Tryptic and chymotroptic peptides were isolated and characterized from cyanogen bromide fragments 1 to 4 of streptococcal proteinase and subjected to sequence analysis by the Edman degradation, carboxy-peptidase digestion, and hydrolytic regeneration of the amino acid residues from the phenylthiocarbamyl derivatives. The results, together with the sequence data of the cyanogen bromide fragment 5 reported in the accompanying papers, provide the structural formula of streptococcal proteinase.

Amino Acid Sequence↗

PubMed1976

Primary structure of streptococcal proteinase. II. Isolation, composition, and amino acid sequences of the tryptic and chymotryptic peptides of cyanogen bromide fragment 5.

The amino acid sequence of the cyanogen bromide fragment 5 of streptococcal proteinase has been determined. This fragment comprises residues 130 to 253 of the proteinase chain. Six tryptic peptides were isolated from maleylated cyanogen bromide fragment 5, and their alignment was obtained by the overlap of chymotryptic peptides. Sequence analysis of tryptic, chymotryptic, and thermolysin peptides was performed by the 5-deimethylaminoaphthalene-1-sulfonyl technique and carboxypeptidases digestion.

Amino Acid Sequence↗

PubMed1976

Primary structure of streptococcal proteinase. III. Isolation of cyanogen bromide peptides: complete covalent structure of the polypeptide chain.

The following sequence has been derived for streptococcal proteinase. (See article). The sequence permits the assignment of the single cysteine residue essential for catalytic action at position 47 from the NH2 terminus of the protein. The tryptophan residue at the binding site of the enzyme is at position 214. A histidine residue at position 195 has been assigned as the catalytically important entity in the molecule. Streptococcal proteinase and papain, an enzyme with similar properties, are compared with respect to structure and function.

Amino Acid Sequence↗

PubMed1976

Complete amino acid analysis of proteins from a single hydrolysate.

An analytical procedure which affords the precise amino acid composition of a protein or a peptide from a single hydrolysate is described. This method utilizes 4 N methanesulfonic acid containing 0.2% 3-(2-aminoethyl)indole, rather then 6N HCl as a catalyst for hydrolysis. The hydrolysis is carried out in vacuo (20 mu) at 115 degrees for 22 to 72 hours. Half-cystine is determined as S-sulfocysteine by treating the hydrolysate with dithiothreitol followed by an excess of tetrathionate. The values of all amino acids, including tryptophan and half-cystine, were close to the expected theoretical values for the proteins examined. The method has the advantage that the neutralized hydrolysate can be applied directly to an ion exchange column. Further, the method is capable of distinguishing between free sulfhydryl groups as S-carbosymethylcysteine and disulfides as S-sulfocysteine. A limitation of the procedure is that tryptophan remains sensitive to the presence of carbohydrate in the sample.

Amino Acids↗

PubMed1976

Bacillus pumilus polysaccharide cross-reactive with meningococcal group A polysaccharide.

A polysaccharide, antigenically and structurally related to meningococcal group A polysaccharide, was isolated from Bacillus pumilus Sh-17. This enteric bacterium has been implicated as a source of natural meningococcal group A immunity (Myerowitz et al., 1973). The B. pumilus polysaccharide was composed of a homopolymer of (1-6)-N-acetyl-manosamine-1-phosphate, glycerol phosphate teichoic acid-containing N-acetylglucosamine and alkali-labile alanine esters, and a mucopeptide. The cross-reaction was due to the poly-(1-6)-N-acetyl-mannosamine-1-phosphate in the B. pumilus and the meningococcal group A polysaccharides, based on the following evidence. Both polysaccharides contained N-acetyl-mannosamine phosphate. Periodate oxidized the mannosamine phosphate residues of the polysaccharide and destroyed their precipitating activity with meningococcal group A antiserum. Mild acid treatment released phosphomonoesters and destroyed the meningococcal group A precipitating activity of both polysaccharides. N-acetyl-mannosamine-6-phosphate inhibited the precipitation reaction between strain Sh-17 and meningococcal group A antisera. Only mannosamine phosphate was detected in trichloroacetic acid extracts of Sh-17 polysaccharide and meningococcal group A antigen-antibody precipitates.

Amino Acids↗

PubMed1975

Cross-reactive antigens and immunity to diseases caused by encapsulated bacteria.

Antigenic structures may be shared among naturally occurring polymers, including proteins and polysaccharides. Proteins are polymers of amino acids. Cross-reactions between proteins are due to similarities in their overall shape rather than their individual amino acid components. Cross-reactions have been demonstrated among proteins with similar evolutionary development and structure, such as serum albumins or immunoglobulins. Polysaccharides are polymers of monosaccharides. In contrast to proteins, antigenic specificities may be conferred by mono-, di-, and trisaccharides. Since there are about 150 known naturally occurring monosaccharides, it is not unexpected that cross-reactions are demonstrable between polysaccharides from widely divergent sources.

Adult↗

PubMed1974