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N Q Lin

Publications and source records attributed to N Q Lin.

4 recordsLinked to original sources
PubMed1994

Protein crystallization in space.

The microgravity environment of space is an ideal place to study the complicated protein crystallization process and to grow good-quality protein crystals. A series of crystal growth experiments of 10 different proteins was carried out in space on a Chinese re-entry satellite FSW-2 in August, 1992. The experiments were performed for about two weeks at a temperature of 18.5 +/- 0.5 degrees C using a tube-like crystallization apparatus made in the Shanghai Institute of Technical Physics, Academia Sinica. More than half of 48 samples from 6 proteins produced crystals, and the effects of microgravity on protein crystal growth were observed, especially for hen-egg white lysozyme and an acidic phospholipase A2 from the venom of Agkistrodon halys Pallas. Analyses of the crystallization of these two enzymes in this mission showed that the microgravity environment in space may be beneficial to improve size, external perfection, morphology, internal order, and nucleation of protein crystals. Some of these positive microgravity effects were also demonstrated by the growth of protein crystals in gelled solution with the above two enzymes. A structural analysis of the tetragonal lysozyme crystal grown in space is in progress.

Ancrod↗
PubMed1985

The complete amino-acid sequence of the proteinase inhibitor B from the root of the arrowhead (Sagittaria sagittifolia L.).

After reduction and alkylation of the disulfide bonds of the proteinase inhibitor B from the root of the arrowhead (Sagittaria sagittifolia L.) followed by CNBr cleavage three peptide fragments with 68, 62 and 11 amino-acid residues could be separated on DEAE-Sepharose CL-6B. The peptides or the inhibitor itself were further specifically cleaved either by trypsin or by the mixture of (CH3)2SO/HCl/HBr at the arginyl- and the tryptophyl-peptide bond, respectively. The complete amino-acid sequences of the peptides were determined by manual solid phase DABITC/PITC double coupling micro-method and the primary structure of the arrowhead inhibitor B consisting of 141 amino-acid residues was then elucidated. Twenty pairs of amino-acid residues are repeated in the molecule of this inhibitor, three of these pairs even occur three times. The possible locations of the reactive sites are discussed. On the basis of sequence comparisons between this inhibitor and all other serine proteinase inhibitors the arrowhead inhibitor may belong to a new family.

Amino Acid Sequence↗
PubMed1984

Purification, characterization and sequence determination of a double-headed trypsin inhibitor peptide from Trichosanthes kirilowii (a Chinese medical herb).

A double-headed trypsin inhibitor peptide was isolated and purified from the root of Trichosanthes kirilowii Maxim (Cucurbitaceae), a Chinese medical herb, by 2.5% trichloroacetic acid and heat treatment followed by affinity chromatography with immobilized trypsin and ion-exchange chromatography. This inhibitor, consisting of 41 amino-acid residues with three pairs of disulfide bonds was sequenced. Two active domains were found to be located at two disulfide loops composed of eight (Pos. 17-24) and nine (Pos. 29-37) amino-acid residues, respectively. It inhibits two molecules of trypsin simultaneously and might be regarded as the smallest double-headed trypsin inhibitor (Mr = 4575) so far known. The chemical modification of the inhibitor with cyclohexandione and citraconic anhydride showed that Arg20-Gly21 and Lys30-Leu31 corresponded to the two reactive sites, respectively. The discovery of the Trichosanthes inhibitor is of importance not only for the study on the structure-function relationship of proteinase inhibitor peptides but also for the search for low molecular mass inhibitors of clinical value among Chinese medical herbs.

Amino Acid Sequence↗