Enzyme stabilizer DTT catalyzes nitrilase analogue hydrolysis of nitriles

Amides are the dominating products in some nitrilase catalyzed conversions of alpha-activated nitriles, but unexpectedly this hydrolytic reaction is also catalyzed by 1,4-dithio-dl-threitol (DTT), a standard antioxidizing enzyme stabilizer.     

Oligodeoxynucleotide analogues containing 3′-deoxy-3′-C-threo-hydroxymethylthymidine: Synthesis, hybridization properties and enzymatic stability

Novel Oligodeoxynucleotide analogues containing 3′-C-threo-methylene phosphodiester internucleoside linkages were synthesized on automated DNA-synthesizers using the phosphoramidite approach. The sugar modified phosphoramidite building block 5 was obtained by phosphitylation of 1-(2,3-dideoxy-5-O-(4,4′-dimethoxytrityl)-3-C-hydroxymethyl-β-D-threo-pentofuranosyl)thymine (4) which was synthesized in only three steps from 5′-O-(4,4′-dimethoxytrityl)thymidine (1). The hybridization properties and enzymatic stability of the oligonucleotide analogues were studied by UV experiments. 17-Mers having one or three modifications in the middle or two modifications in each end hybridized to DNA with moderate lowered affinity compared to unmodified 17-mers (ΔT_m 1–3°C per modification). Furthermore, the end-modified and all-modified oligonucleotides were stable towards snake venom phosphodiesterase.     

Synthesis and microbial transformation of β-amino nitriles

Rhodococcus equi A4, Rhodococcus erythropolis NCIMB 11540 and Rhodococcus sp. R312 were investigated towards their ability to produce β-amino amides and acids from β-amino nitriles. The microorganisms show comparable trends: five-membered alicyclic 2-amino nitriles were transformed significantly faster than the six-membered compounds and the products of trans-2-amino nitriles (amides and acids) were formed considerably faster than the cis-counterparts (amides). The trans-five membered nitriles gave the amides (1b, 5b) in excellent enantiomeric excess (94-99%), the biotransformation of trans-six membered substrates resulted in the formation of the acid (3c, 7c) in excellent ee (87-99%). The ee's of the cis-compounds were throughout lower. Fifteen new substances were synthesized and characterized in the course of this work.     

Thermal and structural study on the lattice compound 1,4-diammoniumbutane bis(theophyllinate)

Crystalline title compound (1) prepared from aqueous solution of theophylline and 1,4-diaminobutane has been structurally and thermally characterized. Both the two-step TG decomposition curve and elemental analysis of the hexagonal crystals show that it consists of theophylline and 1,4-diaminobutane in 2:1 molar ratio. Actually, presence of one type of both theophyllinate anions and 1,4-diammoniumbutane dication have been indicated by FTIR spectroscopy. The molecular structure of lattice compound (1) has been determined by single crystal X-ray diffraction, where the hydrogen positions have been obtained from differential Fourier maps. It has confirmed that the crystal is really built up from these ionic constituents bound together with an extensive net of hydrogen bonds. The coupled TG-FTIR analysis of the evolved gases has revealed that the diamine is released as a whole molecule in the first decomposition step. Clathrate 1 and the proton migration in it might serve as a structural model of solid aminophylline whose crystal structure is still unknown.     

Zur Reaktion von Derivaten des Thiosemicarbazids mit Bisimidchloriden der Oxalsäure

Summary Arylsubstituted oxalic bis-imidochlorides1 react with thiosemicarbazones of type5 as well as13 to give five-membered-ring heterocycles8,11, and16.¹³C-NMR spectroscopy, chemical methods and X-ray crystallography have been used to investigate the nature of the structures obtained. The¹³C-chemical shifts of13 and imidazolidines16 are correlated with Hammett _p constants and dual substituent parameters to evaluate the transmission of theX substitutent electronic effects via the side-chain iminyl carbon atom into the heterocyclic ring and its neighbouring phenyl groups.

     

A Combined Petrographic and Micro-Raman Study of Meteoritic Microdiamond in ALH-77257 Ureilite and ALH-78113 Aubrite

ABSTRACT

Two diamond-bearing meteorites (ALH-77257 and ALH-78113) were investigated by petrographic microscope and micro-Raman spectroscopy. The meteoritic diamonds can be found in fractures or veins cross-cutting the original minerals (olivine, pyroxene, feldspar) and inside the host minerals. The micro-Raman spectral features of microdiamonds in two studied meteorites are very similar to each other. The diamond peak was found at 1329 in ALH-77257 and 1332 cm^?1 in ALH-78113. Hexagonal diamond was not present. However, we observed the D and G bands of graphite or amorphous carbon at 1322 and 1582 cm^?1 wavenumbers, indicating an origin of the meteoritic microdiamonds by magmatic processes.