Among the variants was a nonconservative substitution of lysine by alanine (K232A), with the lysine-encoding allele being associated with higher milk fat content. Haplotype analysis indicated the lysine variant to be ancestral. Two animals that were typed heterozygous (Qq) at the QTL based on marker-assisted QTLgenotyping were heterozygous for the K232A substitution, whereas 14 animals that are most likely qq at the QTL were homozygous for the alanine-encoding allele. An independent association study in Fleckvieh animals confirmed the positive effect of the lysine variant on milk fat content. We consider the nonconservative K232A substitution to be directly responsible for the QTL variation, although our genetic studies cannot provide formal proof.

Various QTL mapping experiments led to the detection of a QTL in the centromeric region of cattle chromosome 14 that had a major effect on the fat content of milk. Recently, the gene encoding diacylglycerol O-acyltransferase (DGAT1) was proposed to be a positional and functional candidate for this trait. This study investigated the effects of a nonconservative lysine to alanine (K232A) substitution in DGAT1, which very likely represents the causal mutation, on milk production traits. Existing granddaughter designs for Fleckvieh and German Holstein, the two major dairy/dual-purpose breeds in Germany, were used to estimate allele frequencies and gene substitution effects for milk, fat, and protein yield, as well as fat and protein content. A restriction fragment length polymorphism assay was applied to diagnose the K232A substitution in DGAT1. Estimates of the allele frequencies for the lysine-encoding variant were based on maternally inherited alleles in sons and amounted to 0.072 for Fleckvieh and 0.548 for German Holstein. Effects of DGAT1 variants on content traits were pronounced; estimates of the gene substitution effect for the lysine-encoding variant were 0.35 and 0.28% for fat content and 0.10 and 0.06% for protein content in Fleckvieh and German Holstein, respectively. Conversely, negative effects of the lysine variant of -242 to -180 kg for Fleckvieh and -260 to -320 kg for German Holstein were revealed for milk yield from first to third lactation, resulting in enhanced fat yield of 7.5 to 14.8 kg in Fleckvieh and 7.6 to 10.7 kg in German Holstein. For protein yield, however, mainly negative effects of -3.6 to 0.2 kg in Fleckvieh and -4.8 to -5.2 kg in German Holstein were observed. Pearson correlations between residuals of milk yield and content traits were decreased when omitting DGAT1 effects in the analysis, thereby indicating that DGAT1 contributes to negative correlations between these traits. Molecular tests allow for the direct selection among variants; however, the benefits of the alternative alleles depend on economic weights given to the different milk production traits in the breeding goal.

N-alkoxyheterocycles can act as powerful one-electron acceptors in photochemical electron-transfer reactions. One-electron reduction of these species results in formation of a radical that undergoes N-O bond fragmentation to form an alkoxy radical and a neutral heterocycle. The kinetics of this N-O bond fragmentation reaction have been determined for a series of radicals with varying substituents and extents of delocalization. Rate constants varying over 7 orders of magnitude are obtained. A reaction potential energy surface is described that involves avoidance of a conical intersection. A molecular basis for the variation of the reaction rate constant with radical structure is given in terms of the relationship between the energies of the important molecular orbitals and the reaction potential energy surface. Ab initio and density functional electronic structure calculations provide support for the proposed reaction energy surface.

We propose the use of single nucleotide polymorphisms (SNPs) instead of polymorphic microsatellite markers for individual identification and parentage control in cattle. To this end, we present an initial set of 37 SNP markers together with a gender-specific SNP for identity control and parentage testing in the Holstein, Fleckvieh and Braunvieh breeds. To obtain suitable SNPs, a total of 91.13 kb of random genomic DNA was screened yielding 531 SNPs. These, and 43 previously identified SNPs, were subjected to the following selection criteria: (1) the frequency of the minor allele must be larger than 0.1 in at least two of the three examined breeds, and (2) markers should not be linked closely. Allele frequencies were estimated by analysing sequencing traces of pooled DNA or by genotyping individual DNA samples. The selected SNP loci were physically mapped by radiation hybrid mapping or by fluorescence in situ hybridization, and tested against the neutral mutation hypothesis. The presented marker set theoretically allows probabilities of identity less than 10(-13) for individual verification and exclusion powers exceeding 99.99% for parentage testing.

The therapeutic potential of elastin-like polypeptide (ELP) conjugated to therapeutic compounds is currently being investigated as an approach to target drugs to solid tumors. ELPs are hydrophobic polymers that are soluble at low temperatures and cooperatively aggregate above a transition temperature (TT), allowing for thermal targeting of covalently attached drugs. They have been shown to cooperatively transition from a disordered structure to a repeating type II β-turn structure, forming a β-spiral above the TT. Here we present biophysical measurements of the structural, thermodynamic, and hydrodynamic properties of a specific ELP being investigated for drug delivery, ELP[V5G3A2-150]. We examine the biophysical properties below and above the TT to understand and predict the therapeutic potential of ELP-drug conjugates. We observed that below the TT, ELP[V5G3A2-150] is soluble, with an extended conformation consisting of both random coil and heterogeneous β structures. Sedimentation velocity experiments indicate that ELP[V5G3A2-150] undergoes weak self-association with increasing temperature, and above the TT the hydrophobic effect drives aggregation entropically. These experiments also reveal a previously unreported temperature-dependent critical concentration (Cc) that resembles a solubility constant. Labeling ELP[V5G3A2-150] with fluorescein lowers the TT by 3.5°C at 20 μM, whereas ELP[V5G3A2-150] dissolution in physiological media (fetal bovine serum) increases the TT by ∼2.2°C.