Reactivity of radicals generated on irradiation of trans-[Ru(NH3)4(NO2)P(OEt)3](PF6)

The electronic absorption spectrum of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in aqueous solution is characterized by a strong absorption band at 334 nm (lambda(max) = 1800 mol(-1) L cm(-1)). On the basis of quantum mechanics calculations, this band has been assigned to a MLCT transition from the metal to the nitro ligand. Molecular orbital calculations also predict an LF transition at 406 nm, which is obscured by the intense MLCT transition. When trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in acetonitrile is irradiated with a 355 nm pulsed laser light, the absorption features are gradually shifted to represent those of the solventocomplex trans-[Ru(NH(3))(4)(solv)(P(OEt)(3)](2+) (lambda(max) = 316 nm, epsilon = 650 mol(-1) L cm(-1)), which was also detected by (31)P NMR spectroscopy. The net photoreaction under these conditions is a photoaquation of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+), although, after photolysis, the presence of the nitric oxide was detected by differential pulse polarography. In phosphate buffer pH 9.0, after 15 min of photolysis, a thermal reaction resulted in the formation of a hydroxyl radical and a small amount of a paramagnetic species as detected by EPR spectroscopy. In the presence of trans-[Ru(NH(3))(4)(solv)P(OEt)(3)](2+), the hydroxyl radical initiated a chain reaction. On the basis of spectroscopic and electrochemical data, the role of the radicals produced is analyzed and a reaction sequence consistent with the experimental results is proposed. The 355 nm laser photolysis of trans-[Ru(NH(3))(4)(NO(2))(P(OEt)(3)](+) in phosphate buffer pH 7.4 also gives nitric oxide, which is readily trapped by ferrihemeproteins (myoglobin, hemoglobin, and cytochrome C), giving rise to the formation of their nitrosylhemeproteins(II), (NO)Fe(II)hem.     

Proton affinity of methyl peroxynitrate

The equilibrium structures, harmonic vibrational frequencies of methyl peroxynitrate, and structures of protonated methyl peroxynitrate have been investigated using ab initio methods. The methods include the single- and double-excitation quadratic configuration (QCISD) methods and the QCISD(T) method, which incorporates a perturbational estimate of the effects of corrected triple excitation. The lowest-energy gas-phase form of protonated methyl peroxynitrate is a complex between CH3OOH and NO2+. The CH3OOH.NO2+ complex is bound by 22 +/- 2 kcal/mol. The estimated proton affinity of methyl peroxynitrate is 178.8 +/- 3 kcal/mol. A general trend for the proton affinity of ROO-NO2 (peroxynitrates) compounds is discussed.     

Engineered biosynthesis of hybrid macrolide polyketides containing D-angolosamine and D-mycaminose moieties

The glycosylation of natural product scaffolds with highly modified deoxysugars is often essential for their biological activity, being responsible for specific contacts to molecular targets and significantly affecting their pharmacokinetic properties. In order to provide tools for the targeted alteration of natural product glycosylation patterns, significant strides have been made to understand the biosynthesis of activated deoxysugars and their transfer. We report here efforts towards the production of plasmid-borne biosynthetic gene cassettes capable of producing TDP-activated forms of D-mycaminose, D-angolosamine and D-desosamine. We additionally describe the transfer of these deoxysugars to macrolide aglycones using the glycosyl transferases EryCIII, TylMII and AngMII, which display usefully broad substrate tolerance.     

Hardware-accelerated protein identification for mass spectrometry

An ongoing issue in mass spectrometry is the time it takes to search DNA sequences with MS/MS peptide fragments (see, e.g., Choudary et al., Proteomics 2001; 1: 651-667.) Search times are far longer than spectra acquisition time, and parallelization of search software on clusters requires doubling the size of a conventional computing cluster to cut the search time in half. Field programmable gate arrays (FPGAs) are used to create hardware-accelerated algorithms that reduce operating costs and improve search speed compared to large clusters. We present a novel hardware design that takes full spectra and computes 6-frame translation word searches on DNA databases at a rate of approximately 3 billion base pairs per second, with queries of up to 10 amino acids in length and arbitrary wildcard positions. Hardware post-processing identifies in silico tryptic peptides and scores them using a variety of techniques including mass frequency expected values. With faster FPGAs protein identifications from the human genome can be achieved in less than a second, and this makes it an ideal solution for a number of proteome-scale applications.     

Über die Struktur der Thioamide und ihrer Derivate—XXIII: 14N-Entkoppelte H-NMR-Spektren und Messung der Rotationsbarrieren bei primären Amiden und Thioamiden

By saturation of the ¹⁴N resonance, hindered internal rotation around the CN bond of the (thio)amide system is detected in the H-NMR spectra of the primary amides ( 1a to 1d ) and the thioamides ( 2a to 2g ). With the aid of coupling constants and benzene dilution shifts, it is possible to assign the signals of the amino group to the cis and the trans NH protons. From coalescence results free enthalpies of activation of hindered internal rotation are obtained, and their dependence on steric and electronic effects as well as the influence of the solvent are discussed.     

Quantitative Bestimmung von Nitroprussiat durch Einwirkung von Tetracyanonickelat

Ohne Zusammenfassung     

A safer substitute for benzidine in the detection of blood

The derivation and synthesis of 3,5,3′,5′-tetramethyl benzidine are described. Prolonged subcutaneous administration to rats gave a negligible yield of tumours, unlike benzidine and o-tolidine with which it was compared. It is a sensitive and specific agent for the detection of blood, and could displace the use of these substances for that purpose.     

Richards' assumptions and Hassler's presumptions

Investigation suggests that certain assumptions must be implicitly made whenever the wellknown and much admired Richards-Hassler methodology (for investigating flow phenomena in multiphase saturated porous media) is being employed. Whenever the propositions that are being taken for granted are not fully stated, however, they can take on the appearance of being presumptions. The analysis presented in this essay, therefore, is intended to clarify the differences between what historically has been said, and what still needs to be said, about the rationale that underlies the sense of the always intriguing but sometimes misunderstood Richards-Hasslet conceptualizations.