Cypridina bioluminescence: light-emitting oxyluciferin-luciferase complex.

Fluorescence of Cypridina oxyluciferin is greatly enhanced when it is bound to luciferase; the spectrum is thereby shifted, so that it corresponds precisely to the emission spectrum characteristic of the bioluminescentoxidation of luciferin. Thus the oxyluciferin-luciferase complex is the lightemitter. The binding is equimolar, with dissociation constant K(D) equal to 3x 10(-7) mole per liter. The molecular weight of the luciferase, according to three different methods, is between 52,000 and 57,000; molecular activities of luciferase for the bioluminescence reaction and for the hydrolysis of oxy-luciferin are 1600 and 2 per minute, respectively.

Studies on beta-lactam antibiotics. XI. Synthesis and structure-activity relationships of new 3-(2,2-dihalovinyl)cephalosporins.

The synthesis and in vitro antibacterial activity of 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2-carboxymethoxyiminoacetamido]- 3-(2,2-dihalovinyl)cephalosporins are described. 3-(2,2-Dihalovinyl)cephalosporins exhibited excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria, especially showed higher activity against Staphylococcus aureus than the corresponding 3-vinylcephalosporin.

Studies on beta-lactam antibiotics. XII. Synthesis and activity of new 3-ethynylcephalosporin.

The synthesis of the orally absorbed 3-ethynylcephalosporin is described. In addition, the structure-activity relationships and oral absorption in rats of 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2- carboxymethoxyiminoacetamido]cephalosporins having various aliphatic hydrocarbon groups at the 3-position are discussed. Of these cephalosporins, 3-ethynyl-cephalosporin exhibited better activity against Staphylococcus aureus than the other cephalosporins and showed moderate oral absorption in rats.

Studies on beta-lactam antibiotics. VII. Effect on antibacterial activity of the oxime O-substituents with various functional groups in the 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2-oxyiminoacetamido]cephalosporins.

The synthesis and in vitro activity of the 7-[O-substituted oxyiminoacetamido]cephalosporins (I) without substitution at 3-position of a cephem nucleus are described. Effect of changing the oxime O-substituents (R1) with various functional groups in the 7-acyl residue on antibacterial activity was examined. Against Gram-positive bacteria, cephems with hydrophilic functions in the R1 moiety such as hydroxyethyl, aminoethyl and carboxymethyl groups showed decrease of the activity, while cephems with lipophilic functions such as cyanomethyl, methylthiomethyl and halogenoethyl groups exhibited increase of the activity. However, influence of the substituents (R1) on activity against Gram-negative bacteria was observed to be relatively independent of the nature of their functional groups.

Studies on beta-lactam antibiotics. II. Synthesis and structure-activity relationships of alpha-hydroxyiminoarylacetyl cephalosporins.

The synthesis and antibacterial activity in vitro of the 2-aryl-2-hydroxyiminoacetyl cephalosporins (2) are described. Within this cephalosporin series, analogs (9f approximately 13f) with 2-hydroxyimino-2-(3-hydroxyphenyl)acetyl group at the 7-position of a cephem nucleus were found to have the highest antibacterial activity against a wide-range of microorganisms, including beta-lactamase-producing bacteria. Structure-activity relationships of 2 are discussed.

Studies on beta-lactam antibiotics. IX. Synthesis and biological activity of a new orally active cephalosporin, cefixime (FK027).

The synthesis and some biological properties of 7 beta-[(Z)-2-(2-amino-4-thiazolyl)-2-(carboxymethoxyimino) acetamido]-3-vinyl-3-cephem-4-carboxylic acid (3, FK027) are described. Diphenylmethyl 7-amino-3-vinyl-3-cephem-4-carboxylate hydrochloride (8), the cephem precursor to FK027 was prepared from 7-aminocephalosporanic acid (7-ACA) by two parallel routes differing primarily in the protection of the 7-amino group. Compound 8 was alternatively prepared from deacetylcephalosporin C sodium salt (DCCNa) with improved yields. Two pathways for the conversion of 8 to FK027 are provided. The new orally active cephalosporin, FK027, possesses a widely expanded antimicrobial activity and high stability to beta-lactamases.

Studies on beta-lactam antibiotics VIII. Structure-activity relationships of 7 beta-[(Z)-2-carboxymethoxyimino-2-arylacetamido]-3-cephem- 4-carboxylic acids.

The synthesis, antimicrobial activity and oral absorptivity of 7 beta-[(Z)-2-carboxymethoxyimino-2-arylacetamido]-3-cephem-4- carboxylic acids are described. The [(Z)-2-(2-amino-4-thiazolyl)-2-carboxymethoxyimino]acetyl group was selected as the most suitable 7-substituent from seven 7-acyl groups for our further investigation of orally active cephalosporins.

Properties and reaction mechanism of the bioluminescence system of the deep-sea shrimp Oplophorus gracilorostris.

The bioluminescent reaction of Oplophorus takes place when the oxidation of coelenterazine (the luciferin) with molecular oxygen is catalyzed by Oplophorus luciferase, resulting in light of maximum intensity at 462 nm and the products CO2 and coelenteramide. Oplophorus luciferase has now been obtained in a highly purified state. Optimum luminescence occurs at pH 9 in the presence of 0.05--0.1 M NaCl at 40 degrees C, and, due to the unusual resistance of this enzyme to heat, visible luminescence occurs at temperatures above 70 degrees C when partially purified enzyme is used. The specific activity of purest preparations is 1.75 X 10(15) photons s-1 mg-1 at 23 degrees C. At pH 8.7, native luciferase has a molecular weight of approximately 130 000, apparently comprising 4 monomers of 31 000; at lower pHs, the native luciferase tends to polymerize. The quantum yield of coelenterazine is 0.34 at 22 degrees C with this enzyme. After the luminescent reaction, the spent solution is nonfluorescent, and likewise solutions of luciferase alone. When the bioluminescent reaction was carried out in the presence of 18O2, the product CO2 contained more than 50% C18O16O, supporting the dioxetane mechanism, but without ruling out the linear peroxide mechanism.