Spin-Lattice Relaxation in Metal-Organic Platinum(II) Complexes

The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II) compounds is studied. Often, such systems are characterized by pronounced zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions for the Orbach slr process do not allow to treat such splitting patterns properly. We discuss the behavior of a modified Orbach expression for a model system and present results of a fit of the temperature dependence of the spin-lattice relaxation rate of Pt(2-thpy)$_2$ based on the modified expression.Comment: 9 pages, 3 figures (made from 4 .eps files), elsart.cls. Using dvips (dvipsk 5.58f), it may be necessary to manually edit the generated file letter.ps to change in the first line from PS-Adobe-2.0 to PS-Adobe-3.0. Chemical Physics Letters, in pres

Tracer sensitive tapes

A leak detection system has been developed, consisting of a tape that can be wrapped around possible leak sites on a system pressurized with air or gaseous nitrogen. Carbon monoxide, at a level of 100 to 1000 parts per million is used as a trace gas in the pressurized system. The sensitive element of the tape is palladium chloride supported on specially prepared silica gel and specially dried. At a CO level of 100 ppm and a leak rate of 10-20 ml/hr, discoloration of the sensitive element is observed in 1.5 to 3 min. The tape and trace gas are compatible with aerospace hardware, safe to handle, and economically reasonable to produce and handle

Localization, analysis and evolution of transposed human immunoglobulin VK genes

The localization of Vκ gene regions to chromosome 2, on which the κ locus is located, and to other chromosomes is described. The Vκ genes that have been transposed to other chromosomes are called orphons. The finding of two new Vκ genes on chromosome 22 is reported. A Vκ II gene of this region and two Vκ I genes of the Chr 1 and the cos 118 regions were sequenced. The two Vκ I orphon sequences and two others that had been determined previously were 97.5% identical, indicating that they may have evolved from a common ancestor by amplification. A model of the evolution of the human Vκ orphons is discussed. Author Keywords: Human-rodent cell hybrids; cosmids; restriction maps; ligation artifacts; orphon; recombinant DNA Abbreviations: aa, amino acid(s); bp, base pair(s); Chr1, Vκ gene-containing regions of chromosomes 1; Chr22, Vκ gene-containing regions of chromosomes 22; FR, framework regions; CDR, complementary determining regions; kb, kilo-base(s) or 1000 bp; L, L′, parts of a leader gene segment; m219-1, the first subclone of the cosmid clone cos 219; orphon, Vκ gene outside the κ locus on chromosome 2pl2; SSC, 0.15 M NaCl, 0.015 M Na3-citrate, pH 7.6; V, variable gene segments; J, joining gene segments; C, constant gene segments; Vκ I to Vκ IV, variable gene segments of immunoglobulin light chains of the κ type belonging to subgroups I to IV; for reasons of simplicity Vκ gene segments are generally called Vκ gene

Precursors of Cytochrome Oxidase in Cytochrome-Oxidase-Deficient Cells of Neurospora crassa

Three different cell types of Neurospora crassa deficient in cytochrome oxidase were studied: the nuclear mutant cni-1, the cytoplasmic mutant mi-1 and copper-depleted wild-type cells. * 1. The enzyme-deficient cells have retained a functioning mitochondrial protein synthesis. It accounted for 12–16% of the total protein synthesis of the cell. However, the analysis of mitochondrial translation products by gel electrophoresis revealed that different amounts of individual membrane proteins were synthesized. Especially mutant cni-1 produced large amounts of a small molecular weight translation product, which is barely detectable in wild-type. * 2. Mitochondrial preparations of cytochrome-oxidase-deficient cells were examined for precursors of cytochrome oxidase. The presence of polypeptide components of cytochrome oxidase in the mitochondria was established with specific antibodies. On the other hand, no significant amounts of heme a could be extracted. * 3. Radioactively labelled components of cytochrome oxidase were isolated by immunoprecipitation and analysed by gel electrophoresis. All three cell types contained the enzyme components 4–7, which are translated on cytoplasmic ribosomes. The mitochondrially synthesized components 1–3 were present in mi-1 mutant and in copper-depleted wild-type cells. In contrast, components 2 and 3 were not detectable in the nuclear mutant cni-1. Both relative and absolute amounts of these polypeptides in the enzyme-deficient cells were quite different from those in wild-type cells. * 4. The components of cytochrome oxidase found in the enzyme-deficient cells were tightly associated with the mitochondrial membranes. * 5. Processes, which affect and may control the production of enzyme precursors or their assembly to a functional cytochrome oxidase are discussed