RESUMO
For Pd/Pd(111) an exceptionally high barrier (350 meV) for surface self-diffusion and a negative additional energy DeltaE = -53 meV for step-down diffusion are measured. Both findings agree with the proposed role of free-electron-like surface states. Despite the negative value of DeltaE layer-by-layer growth is not observed. This is related to the low preexponential factor for step-down diffusion. Preadsorption of oxygen increases DeltaE but flattens the films. Again this is due to the prefactors for diffusion. The present results demonstrate the importance of entropic effects for diffusion and growth.
RESUMO
We cloned and sequenced a composite cDNA corresponding to the 2.6 kb last instar-specific, juvenile hormone-suppressible Lhp82 mRNA from Galleria mellonella. The identity of the cDNA was confirmed by N-terminal amino acid sequencing of the purified Lhp82 subunit. In addition, we sequenced all coding regions and most of the intronic DNA as well as 1300 nucleotides of 5' flanking DNA from the Lhp82 gene. The eight exons of the Lhp82 gene specify a pre-protein of 706 residues, including the signal peptide of 18 amino acids. The deduced amino acid sequence of Lhp82 contains four potential N-glycosylation sites, and the calculated isoelectric point and molecular weight of secreted Lhp82 are pI = 6.43 and 79.9 kDa, respectively. Inspection of the 5' flanking and intronic regions of Lhp82 DNA revealed a 301 nucleotide cassette in intron 6 that appears to be a recently inserted repetitive element. We also performed Northern blot and nuclear run-off transcription experiments in order to determine the basis for Lhp82 gene inactivity after day 2 of the pupal stage. The results of these studies indicate that Lhp82 transcription is permanently shut off by the ecdysteroid pulse which occurs in the absence of juvenile hormone beginning 24 h post-pupation.
Assuntos
Proteínas de Drosophila , Genes de Insetos , Hormônios de Inseto/genética , Proteínas de Insetos , Mariposas/genética , Sequência de Aminoácidos , Aminoácidos/análise , Animais , Sequência de Bases , Clonagem Molecular , Primers do DNA/genética , DNA Complementar/genética , Éxons , Regulação da Expressão Gênica , Genes de Insetos/efeitos dos fármacos , Hormônios de Inseto/química , Íntrons , Hormônios Juvenis/farmacologia , Dados de Sequência Molecular , Peso Molecular , Mariposas/crescimento & desenvolvimento , Conformação Proteica , Homologia de Sequência de AminoácidosRESUMO
The metabolites of gold in the urine of rats given the antiarthritic drug aurothiomalate were investigated by gel permeation chromatography, electrophoresis, and chemical studies. Following a single dose of aurtothiomalate, the excreted gold was protein-bound in the high-molecular-weight (greater than or equal to 150,000 dalton) and serum albumin fractions. Electrophoresis confirmed the presence of albumin, but showed that the other proteins present differ from those in normal or in vitro aurothiomalate-incubated rat sera. The pattern of the proteins establishes that the proteinuria was of the glomerular type. The alterations in the gold distribution produced by incubation of the urine with the low-molecular-weight thiol penicillamine and with exogenously added aurothiomalate indicated the existence of a labile equilibrium of gold among protein binding sites in the urine. Incubation of rat and human sera and commercially prepared serum albumins with aurothiomalate increased the electrophoretic mobility of the albumin. The significance of this change in electrophoretic mobility with respect to two models of gold binding by serum albumin is discussed.
