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B L Chen

Publications and source records attributed to B L Chen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Low-temperature unfolding of a mutant of phage T4 lysozyme. 2. Kinetic investigations.

A disulfide-bridged variant of bacteriophage T4 lysozyme has been found to undergo a low- as well as high-temperature unfolding transition in guanidinium chloride [see Chen and Schellman (1989)]. The kinetics for this process have been followed for several temperatures, a range of guanidinium chloride concentrations, and a number of values of pH. Microscopic rate constants for protein unfolding and refolding were extracted from these data to explore the nature of the cold unfolding transition. The data were interpreted using transition-state theory. It was found that the Arrhenius energy is temperature dependent. The transition state is characterized by (1) a high energy and low entropy compared to the native state, (2) a heat capacity which is closer to the native state than to the unfolded state, and (3) a low exposure to solvent compared to the unfolded state, as judged by its interaction with guanidinium chloride. With increasing concentration of guanidinium chloride, the low-temperature unfolding rate increases strongly, and the refolding rate decreases very strongly.

Escherichia coli↗
PubMed1985

Effects of anordrin and its analogue on antifertility.

Anordrin has been used as an effective postcoital contraceptive in China. The mechanism of anordrin and its analogue SIPPR-113 on antifertility has been studied. Anordrin and SIPPR-113 possessed estrogenicities and induced decrease in serum progesterone levels in rats. Their antiprogesterone activities might be mainly caused by their estrogenicities, which were the main but not the only contributors for the antifertility. The direct effects of anordrin and SIPPR-113 on human trophoblast cells were studied. A concentration of 50 micrograms/ml or 100 micrograms/ml of anordrin or SIPPR-113 could injure the human trophoblast cells in vitro. The uterine Pontamine blue reaction of mated rats was inhibited in those treated with anordrin or SIPPR-113 at the dose of 4 mg/kg. Anordrin, SIPPR-113 or AF-45 was given orally, intramuscularly and intravenously. The effects of drugs administered via the three routes were nearly the same. This study further demonstrated that anordrin was hydrolyzed to break its bond of dipropionate and was transformed into its parent steroid AF-45 to exert its antifertility effects in vivo. This study warrants that anordrin should been evaluated further.

Administration, Oral↗
PubMed1978

Amino acid sequence of the human myeloma lambda chain Win.

The complete amino acid sequence of the variable region of a human myeloma immunoglobulin light chain (Win) has been determined. The sequence of the constant region has been verified by compositional analysis of its tryptic peptides. The amino acid sequence of the light chain Win corresponds to sub group II and shows no unusual amino acid replacements in its constant or variable regions when compared to other human gamma chains.

Amino Acid Sequence↗
PubMed1977

Amino acid sequence of the VH region of a human myeloma immunoglobulin (IgG New).

The amino acid sequence of the heavy-chain variable region of the human immunoglobulin. New has been determined. Since the amino terminus of the heavy chain was blocked, the sequence of residues 1-69 was established by digesting the appropriate CNBr fragment separately with trypsin, chymotrypsin, and thermolysin and sequencing the resulting peptides. The region from residues 70 to 120 was present in another CNBr fragment which was submitted directly to automatic Edman degradation. The result of this experiment extended the sequence to residue 100. The primary structure of the remaining portion of the VH region was determined by automatic Edman degradation of a lysine-blocked tryptic peptide derived from this region which included residues 98-214. The sequence of the VH region of New corresponds most closely to VH sequences of proteins in the VH II subgroup. This primary structure makes it possible to construct a model from the high-resolution electron-density map of protein New.

Amino Acid Sequence↗
PubMed1975

Structure and specificity of antibody molecules.

The structure of the Fab' fragment of a human myeloma protein (IgG1 (lambda) New) has been determined by X-ray crystallographic analysis to a nominal resolution of 0.2 nm. Each of the structure subunits corresponding to the variable and to the constant homology regions of the light and heavy polypeptide chains contains two irregular beta-sheets which are roughly parallel to each other and surround a tighly packed interior of hydrophobic side chains. The regions of the hypervariable sequences in the light and heavy chains occur in close spatial proximity at one end of the molecule, defining the active site of IgG New. The role of these hypervariable regions in defining the size and shape of the active site of different immunoglobulins is discussed on the basis of the three-dimensional model of Fab' New. Several ligands that bind to the active centre of IgG New have been used to obtain crystalline ligand-Fab' New complexes which were investigated by difference Fourier maps. These studies are analysed in terms of the biological function and specificity of antibodies.

Amino Acid Sequence↗
PubMed1974

The three-dimensional structure of the fab' fragment of a human myeloma immunoglobulin at 2.0-angstrom resolution.

The structural analysis of the Fab' fragment of human myeloma immunoglobulin IgGl(lambda) New has been extended to a nominal resolution of 2.0 A. Each of the structural subunits corresponding to the variable and to the constant homology regions of the light and heavy chains contains two irregular beta-sheets which are roughly parallel to each other and surround a tightly packed interior of hydrophobic side chains. About 50-60% of the amino-acid residues are included in beta-pleated sheets. Sequence alignments between the homology regions of Fab' New obtained by comparison of their three-dimensional structures are given. Some of the sequence variations observed in light and heavy chains and the role of the regions of hypervariable sequence in defining the size and shape of the active site of different immunoglobulin molecules are discussed on the basis of the three-dimensional model of Fab' New.

Amino Acid Sequence↗
PubMed1973

Three-dimensional structure of the Fab' fragment of a human immunoglobulin at 2,8-A resolution.

The structure of the Fab' fragment of a human myeloma immunoglobulin was determined by x-ray crystallographic analysis at 2.8-A resolution. The Fourier map of the electron density was correlated with the aminoacid sequence to obtain a three-dimensional model. Four globular subunits, which correspond to the homology regions of the light and heavy chains, are arranged in a tetrahedral configuration. These subunits closely resemble each other, sharing a basic pattern of polypeptide chain folding. In each subunit, long sequences of tightly packed, hydrogen bonded polypeptide chain run parallel to the major axis of the subunit. No helical conformation can be seen. Different patterns of interchain disulfide linkage and unusual intrachain disulfide bonds that have been observed in other immunoglobulins can be explained with this model. The regions of hypervariable sequences in the light and heavy chains occur at one end of the molecule, in close spatial proximity.

Amino Acid Sequence↗