Transport of low molecular weight substances in protein crystals and films

Diffusion of synthetic dyes in lysozyme crystals and bovine serum albumin (BSA) amorphous films is shown to depend on the size of diffusate molecule far more strongly than in solutions. The diffusion coefficient increases from 10(-8) to 10(-13) cm2 sec-1 on about 1.5 divided by 2--fold increase in diffusate dimensions, the diffusion being completely arrested on reaching the limiting dimensions of about 14 A and 12 A for BSA films and lysozyme crystals, respectively. The diffusion in lysozyme crystals is anisotropic, with a diffusion maximum directed along their screw axes. The diffusion coefficient dependence on the charge of diffusate and its binding to proteins is discussed.     

Antibacterial substances of low molecular weight isolated from the blowfly, Lucilia sericata

Low molecular weight compounds were isolated by high-performance liquid chromatography from the maggot or haemolymph extracts of Lucilia sericata (Meigen) (Diptera: Calliphoridae). Using gas chromatography-mass spectrometry analysis, three compounds were obtained: p-hydroxybenzoic acid (molecular weight 138 Da), p-hydroxyphenylacetic acid (molecular weight 152 Da) and octahydro-dipyrrolo[1,2-a;1',2'-d] pyrazine-5,10-dione (molecular weight 194 Da), also known as the cyclic dimer of proline (or proline diketopiperazine or cyclo[Pro,Pro]). All three molecules revealed antibacterial activity when tested against Micrococcus luteus and/or Pseudomonas aeruginosa, and the effect was even more pronounced when these molecules were tested in combination and caused lysis of these bacteria.     

Application of the dansylation reaction to the characterization of low molecular weight peptides by dodecyl sulfate-polyacrylamide-gel electrophoresis.

Polyacrylamide-gel electrophoresis of low molecular weight DNS-peptides was performed in the presence of 0.1% sodium dodecyl sulfate and 8 m urea. This procedure enabled an estimation of the molecular weight of peptides at the nanomole level without staining. A linear relationship between molecular weight and mobility was obtained over a molecular weight range of 1,000–12,000, although a few anomalous peptides (e.g., glucagon and insulin) and small peptides of molecular weight less than 1,000 deviated from linearity. The N-terminal amino acid of a peptide can be determined in combination with thin layer chromatography on polyamide sheets. The usefulness of this procedure for checking small amounts of contaminant in an oligopeptide sample was also noted.     

Chromatography of carboxylic proteinases on sorbents containing the 2,4-dinitrophenyl group. Role of ionic interactions]

The chromatography of porcine pepsin on biospecific sorbents (Sepharose-4B-epsilon-DNP-aminocapronylhydrazide and Sepharose-4B-N-DNP-N'-acetylhexamethylenediamine) was studied. The sorbents in question differ from the previously used hydrophobic sorbent Sepharose-4B-DNP-hexamethylenediamine by the lack of strongly basic groups in the site of the ligand binding to the polymeric matrix. No qualitative differences in the pepsin chromatography on the three sorbents were observed. Presumably the decrease of the pepsin binding to the sorbents, containing the dinitrophenyl group, at pH values above the isoelectric point may be due to the effects of the salt on the binding site in the enzyme molecule rather than to the screening of the positive charges of the sorbent by chlorine ions. A commercial preparation of pepsin was purified 2-fold on the sorbent Sepharose-4B-epsilon-DNP-animocapronylhydrazide. The synthesis of sorbents is described.     

2,4-Bis(octadecanoylamino)benzenesulfonic acid sodium salt as a novel scavenger receptor inhibitor with low molecular weight

In order to investigate the effect of the fixation of the orientations of the two long chains, three types of novel derivatives of scavenger receptor inhibitor 1 were synthesized, and their biological activities were evaluated. Among the novel derivatives, 2,4-bis(octadecanoylamino)benzenesulfonic acid sodium salt (4d) showed the most potent inhibitory activity against the incorporation of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-labeled acetyl-LDL (DiI-acetyl-LDL) into macrophages. 2,5-Bis(octadecanoylamino)benzenesulfonic acid sodium salt (4c), a regioisomer of 4d, did not exhibit as potent an inhibitory activity as 4d, meaning that the substitution pattern of two long chains on the benzene ring must be important. Compound 4d exhibited 10 times more potent inhibitory activity against the binding of 125I-labeled acetyl-LDL to the surface of macrophages than compound 1.     

Studies on low molecular weight nuclear protein of tumour and normal cells.

1. Preliminary results of comparative electrophoretical and immunological analyses of the components of two classes of non-histone proteins, i.e. NHP1 and NHP2 eluted from hydroxyapatite allowed to suppose that protein of Mw 18,000 is specific for animal tumour cells. 2. However, the studies on cellular distribution of this polypeptide indicated that it is exclusively located in nuclei of hepatoma and normal liver as well. 3. The former observation seems to be the result of changes of the affinity of this protein to DNA during neoplastic transformation.     

Sulfated, low molecular weight lignins inhibit a select group of heparin-binding serine proteases

Sulfated low molecular weight lignins (LMWLs), designed as oligomeric mimetics of low molecular weight heparins (LMWHs), have been found to bind in exosite II of thrombin. To assess whether sulfated LMWLs recognize other heparin-binding proteins, we studied their effect on serine proteases of the coagulation, inflammatory and digestive systems. Using chromogenic substrate hydrolysis assay, sulfated LMWLs were found to potently inhibit coagulation factor XIa and human leukocyte elastase, moderately inhibit cathepsin G and not inhibit coagulation factors VIIa, IXa, and XIIa, plasma kallikrein, activated protein C, trypsin, and chymotrypsin. Competition studies show that UFH competes with sulfated LMWLs for binding to factors Xa and XIa. These results further advance the concept of sulfated LMWLs as heparin mimics and will aid the design of anticoagulants based on their novel scaffold.