Part I. Synthesis of L-amino acid oxidase by a serine- or glycine-requiring strain of neurospora. Part II. Studies concerning multiple electrophoretic forms of tyrosinase in neurospora

<p>Part I: Synthesis of L-Amino Acid Oxidase by a Serine- or Glycine-Requiring Strain of Neurosporap> <p>Wild-type cultures of Neurospora crassa growing on minimal medium contain low levels of L-amino acid oxidase, tyrosinase, and nicotinarnide adenine dinucleotide glycohydrase (NADase). The enzymes are derepressed by starvation and by a number of other conditions which are inhibitory to growth. L-amino acid oxidase is, in addition, induced by growth on amino acids. A mutant which produces large quantities of both L-amino acid oxidase and NADase when growing on minimal medium was investigated. Constitutive synthesis of L-amino acid oxidase was shown to be inherited as a single gene, called P110, which is separable from constitutive synthesis of NADase. P110 maps near the centromere on linkage group IV.p> <p>L-amino acid oxidase produced constitutively by P110 was partially purified and compared to partially purified L-amino acid oxidase produced by derepressed wild-type cultures. The enzymes are identical with respect to thermostability and molecular weight as judged by gel filtration.p> <p>The mutant P110 was shown to be an incompletely blocked auxotroph which requires serine or glycine. None of the enzymes involved in the synthesis of serine from 3-phosphoglyceric acid or glyceric acid was found to be deficient in the mutant, however. An investigation of the free intracellular amino acid pools of P110 indicated that the mutant is deficient in serine, glycine, and alanine, and accumulates threonine and homoserine.p> <p>The relationship between the amino acid requirement of P110 and its synthesis of L-amino acid oxidase is discussed.p> <p>Part II: Studies Concerning Multiple Electrophoretic Forms of Tyrosinase in Neurosporap> <p>Supernumerary bands shown by some crude tyrosinase preparations in paper electrophoresis were investigated. Genetic analysis indicated that the location of the extra bands is determined by the particular T allele present. The presence of supernumerary bands varies with the method used to derepress tyrosinase production, and with the duration of derepression. The extra bands are unstable and may convert to the major electrophoretic band, suggesting that they result from modification of a single protein. Attempts to isolate the supernumerary bands by continuous flow paper electrophoresis or density gradient zonal electrophoresis were unsuccessful.p>

Test particle motion in a Lorentz gas

<p>This is a two-part thesis concerning the motion of a test particle in a bath. In part one we use an expansion of the operator PLep>it(1-P)Lp>LP to shape the Zwanzig equation into a generalized Fokker-Planck equation which involves a diffusion tensor depending on the test particle's momentum and the time.p> <p>In part two the resultant equation is studied in some detail for the case of test particle motion in a weakly coupled Lorentz Gas. The diffusion tensor for this system is considered. Some of its properties are calculated; it is computed explicitly for the case of a Gaussian potential of interaction.p> <p>The equation for the test particle distribution function can be put into the form of an inhomogeneous Schroedinger equation. The term corresponding to the potential energy in the Schroedinger equation is considered. Its structure is studied, and some of its simplest features are used to find the Green's function in the limiting situations of low density and long time.p>

Electronic structure in five-coordinate complexes of nickel(II) with heavy-donor ligands

<p>I.p> <p>Various studies designed to elucidate the electronic structure of the arsenic donor ligand, o-phenylenebisdimethylarsine (diarsine), have been carried out. The electronic spectrum of diarsine has been measured at 300 and 77˚K. Electronic spectra of the molecular complexes of various substituted organoarsines and phosphines with tetracyanoethylene have been measured and used to estimate the relative ionization potentials of these molecules. p> <p>Uv photolysis of arsines in frozen solution (96˚K) has yielded thermally labile, paramagnetic products. These include the molecular cations of the photolyzed compounds. The species (diars)p>+p> exhibits hyper-fine splitting due to two equivalent p>75p>As(I=3/2) nuclei. Resonances due to secondary products are reported and assignments discussed. p> <p>Evidence is presented for the involvement of d-orbitals in the bonding of arsines. In (diars)p>+p> there is mixing of arsenic “lone-pair” orbitals with benzene ring π-orbitals.p> <p>II. p> <p>Detailed electronic spectral measurements at 300 and 77˚K have been carried out on five-coordinate complexes of low-spin nickel(II), including complexes of both trigonal bipyramidal (TBP) and square pyramidal (SPY) geometry. TBP complexes are of the form NiLXp>+p> (X=halide or cyanide,p> <p>L = Qƭ(CH₂)₃As(CH₃)₂]₃ orp> <p>P [hexagon - Q'CH₃] , Q = P, As, p> <p>Q’=S, Se).p> <p>The electronic spectra of these compounds exhibit a novel feature at low temperature. The first ligand field band, which is asymmetric in the room temperature solution spectrum, is considerably more symmetrical at 77˚K. This effect is interpreted in terms of changes in the structure of the complex. p> <p>The SPY complexes are of the form Ni(diars)₂Xp>zp> (X=CL, Br, CNS, CN, thiourea, NO₂, As). On the basis of the spectral results, the d-level ordering is concluded to be xy ˂ xz, yz ˂ zp>2p> ˂˂ xp>2p> - yp>2p>. Central to this interpretation is identification of the symmetry-allowed p>1p>A₁ → p>1p>E (xz, yz → xp>2p> - yp>2p>) transition. This assignment was facilitated by the low temperature measurements. p> <p>An assignment of the charge-transfer spectra of the five-coordinate complexes is reported, and electronic spectral criteria for distinguishing the two limiting geometries are discussed. p>