SQUID-based detection of ultra-low-field multinuclear NMR of substances hyperpolarized using signal amplification by reversible exchange.

Ultra-low-field (ULF) nuclear magnetic resonance (NMR) is a promising spectroscopy method allowing for, e.g., the simultaneous detection of multiple nuclei. To overcome the low signal-to-noise ratio that usually hampers a wider application, we present here an alternative approach to ULF NMR, which makes use of the hyperpolarizing technique signal amplification by reversible exchange (SABRE). In contrast to standard parahydrogen hyperpolarization, SABRE can continuously hyperpolarize 1 H as well as other MR-active nuclei. For simultaneous measurements of 1 H and 19 F under SABRE conditions a superconducting quantum interference device (SQUID)-based NMR detection unit was adapted. We successfully hyperpolarized fluorinated pyridine derivatives with an up to 2000-fold signal enhancement in 19 F. The detected signals may be explained by two alternative reaction mechanisms. SABRE combined with simultaneous SQUID-based broadband multinuclear detection may enable the quantitative analysis of multinuclear processes.

A bidentate boryl ligand: syntheses of platinum and iridium complexes.

A methylenediphenylphosphine substituted diazaborole was obtained in a two-step procedure in amounts around 4 g. This B-P ligand was coordinated at platinum and iridium and the structures of the boryl complexes are discussed. In the case of the iridium derivative an interesting boron-boron contact was found.

Phospholipase A secreted by Legionella pneumophila destroys alveolar surfactant phospholipids.

Destruction of alveolar surfactant phospholipids by bacterial phospholipases is suggested to be a major virulence factor involved in bacterial pneumonia. Since Legionella pneumophila secretes phospholipase A, we analyzed phospholipid degradation in natural bovine surfactant by L. pneumophila. Phospholipids were reduced in amount after incubation with bacteria or culture supernatant of L. pneumophila serogroup 6. Free fatty acids and lysophosphatidylcholine were formed, the latter is known to be highly cytotoxic. Surface tension of surfactant as determined by pulsating bubble surfactometer increased significantly compared to the control. Phospholipase A activity seems to be a powerful agent of legionellae in causing lung disease.

ptGAs--genetic algorithms evolving noncoding segments by means of promoter/terminator sequences.

In this article we present work on chromosome structures for genetic algorithms (GAs) based on biological principles. Mainly, the influence of noncoding segments on GA behavior and performance is investigated. We compare representations with noncoding sequences at predefined, fixed locations with "junk" code induced by the use of promoter/terminator sequences (ptGAs) that define start and end of a coding sequence, respectively. As one of the advantages of noncoding segments a few researchers have identified the reduction of the disruptive effects of crossover, and we solidify this argument by a formal analysis of crossover disruption probabilities for noncoding segments at fixed locations. The additional use of promoter/terminator sequences not only enables evolution of parameter values, but also allows for adaptation of number, size, and location of genes (problem parameters) on an artificial chromosome. Randomly generated chromosomes of fixed length carry different numbers of promoter/terminator sequences resulting in genes of varying size and location. Evolution of these ptGA chromosomes drives the number of parameters and their values to (sub)optimal solutions. Moreover, the formation of tightly linked building blocks is enhanced by self-organization of gene locations. We also introduce a new, nondisruptive crossover operator emerging from the ptGA gene structure with adaptive crossover rate, location, and number of crossover sites. For experimental comparisons of this genetic operator to conventional crossover in GAs, as well as properties of different ptGA chromosome structures, an artificial problem from the literature is utilized. Finally, the potential of ptGA is demonstrated on an NP-complete combinatorial optimization problem.

6 beta-hydroxycortisol in serum and urine as determined by enzyme immunoassay on microtitre plates.

We modified our previous enzyme immunoassay (Clin Chim Acta 1986;157:267-76) for estimating 6 beta-hydroxycortisol (6 beta-OHF) to provide a more routine procedure for measuring it in urine and to increase sensitivity for its measurement in serum. Precision, analytical recovery, specificity, and detection limit are reported. 6 beta-OHF and 17-hydroxycorticosteroids in 24-h and 4-h (08:00-12:00 h) urine collections from healthy volunteers showed no significant day-to-day differences in excretion rate for either collection period. Mean values for 6 beta-OHF in serum of men, women, and women taking oral contraceptives showed no significant differences among these groups.