Molybdenum may function as a catalyst in promoting and controlling some of the complex chemical reactions that go on in living systems. The lack of understanding which exists about these reactions is due to their obvious complexity and to the extremely minute quantities of molybdenum involved. Traces of molybdenum have been shown to have spectacular results on the growth of plants when added to certain soils. This metal is also required for the growth of azobacter, the nitrogen-fixing bacteria.

Thesis (Ph. D.)--Columbia University, 1945. / Vita. "Literature cited": p. 66-67.

Thesis (Ph. D.)--Columbia University, 1945. / Vita. "Literature cited": p. 66-67.

No description available.

O pigmento da carne fresca, oximioglobina, e a sua forma oxidada, metmioglobina, podem ser ambos oxidados pela riboflavina quando expostos à radiação luminosa, afetando sua estabilidade redox da carne do ponto de vista nutricional e sensorial. A reação da MbFe(II)O2 e da MbFe(III) com o estado tripleto da riboflavina, 3Rib, envolve uma eficiente transferência de elétrons entre o anel isoaloxazina da riboflavina e a cadeia polipeptídica da proteína, o que leva à formação de cross-link e/ou fragmentação, como demostrado por SDS-PAGE e Western-blot. A constante global de velocidade para a oxidação da MbFe(II)O2 pela 3Rib é (3,0 ± 0,5 ) 109 L·mol-1·s-1 e de (3,1 ± 0,4) 109 L·mol-1·s-1 para a oxidação da MbFe(III) pelo estado tripleto da riboflavina. Cálculos termodinâmicos demonstram ainda que há formação de um complexo exotérmico com estequiometria 1:1 favorecido a temperaturas mais baixas com Ka = (1.2 ± 0.2) 104 mol·L-1 a 25 °C e ΔHo = -112 ± 22 kJ·mol-1 e ΔSo = -296 ± 75 J·mol-1·K-1. Conclui-se que para carne, a riboflavina é um fotossensibilizador para oxidação de proteína e não para a descoloração. / The fresh meat pigment oxymyoglobin, MbFe(II)O2, and its oxidized form metmyoglobin, MbFe(III), are both oxidized by riboflavin as photosensitizer. The reaction of MbFe(II)O2 and MbFe(III) with triplet-state riboflavin, 3Rib, involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western-blotting, while the heme iron center is not oxidized. The over-all rate constant for oxidation of MbFe(II)O2 by 3Rib is (3.0 ± 0.5) 109 L·mol-1·s-1 and (3.1 ± 0.4) 109 L·mol-1·s-1 for MbFe(III) in aqueous 0.20 mol·L-1 NaCl phosphate buffer of pH 7.4 at 25 °C as determined by transient absorption laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using single photon counting time resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has Ka = (1.2 ± 0.2) 104 mol·L-1 at 25 °C with ΔHo = -112 ± 22 kJ·mol-1 and ΔSo = -296 ± 75 J·mol-1·K-1. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2011. / Eremothecium gossypii has the ability to utilize vegetable oils as a carbon source to produce riboflavin. This organism has been known to produce as much as 40 000 times more riboflavin than it requires after genetic modification on simple sugars. Adaptation of this organism to various oil substrates for riboflavin production has been poorly investigated. The aim of this research was thus to investigate the production of riboflavin by Eremothecium gossypii, on various oils and to improve production by mutating the organism and optimising media components using Design of Experiments (DOE). Nine overproducing mutants were obtained after mutating with various concentrations of ethylmethane sulphonate (EMS), n-methyl-n‟-nitro-n-nitrosoguanidine (MNNG) and Ultraviolet light. Riboflavin overproducing mutants were screened on an itaconate-containing medium; the colonies appeared yellow instead of white in the case of the wild-type. The itaconate screening medium isolated mutants with an isocitrate lyase that was insensitive to feedback inhibition. Mutations performed using EMS increased the ability of E. gossypii to produce riboflavin by 611% (7-fold) compared to the wild-type. This was achieved with soybean oil as a carbon source and was better than the other five oils used. Using DOE, fractional factorial experiments were carried out to optimise media components for riboflavin production on soybean oil. The total riboflavin produced by E. gossypii mutant EMS30/1 increased from 59.30 mg l-1 on a standard O&K medium using soybean oil as a carbon source to 100.03 mg l-1 on a DOE improved O&K medium, a 69% increase. The final optimised growth medium was determined from a central composite design using response surface plots together with a mathematical point-prediction tool and consisted of 5.0 g l-1 peptone, 5.0 g l-1 malt extract, 5.1 g l-1 yeast extract, 0.64 g l-1 K2HPO4, 0.6 g l-1 MgSO4 and 20 g l-1 soybean oil. Fractional factorial and central composite media optimization designs increased riboflavin production by several fold over their iterations. There was an overall increase of 1099% (12-fold) in riboflavin production by the mutant grown in an optimized medium compared to the initial riboflavin produced by the wild-type.

Thesis (Ph. D.)--University of Wisconsin--Madison, 19. / Typescript. Vita. Includes (as Section I): Preparation of samples for microbiological determination of riboflavin / F.M. Strong and L.E. Carpenter. Reprinted from Industrial and engineering chemistry, vol. 14 (15 Nov. 1942), p. 909-913. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1945. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 46-53).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1942. / Part I.A. reprinted from Journal of biological chemistry, vol. 137, no. 1 (Jan. 1941), p. 363-372. Part II. reprinted from Industrial and engineering chemistry, Analytical edition, vol. 13 (15 Aug. 1941), p. 566-570. Remainder typescript. Includes abstract and vita. Includes bibliographical references.

O pigmento da carne fresca, oximioglobina, e a sua forma oxidada, metmioglobina, podem ser ambos oxidados pela riboflavina quando expostos à radiação luminosa, afetando sua estabilidade redox da carne do ponto de vista nutricional e sensorial. A reação da MbFe(II)O2 e da MbFe(III) com o estado tripleto da riboflavina, 3Rib, envolve uma eficiente transferência de elétrons entre o anel isoaloxazina da riboflavina e a cadeia polipeptídica da proteína, o que leva à formação de cross-link e/ou fragmentação, como demostrado por SDS-PAGE e Western-blot. A constante global de velocidade para a oxidação da MbFe(II)O2 pela 3Rib é (3,0 ± 0,5 ) 109 L·mol-1·s-1 e de (3,1 ± 0,4) 109 L·mol-1·s-1 para a oxidação da MbFe(III) pelo estado tripleto da riboflavina. Cálculos termodinâmicos demonstram ainda que há formação de um complexo exotérmico com estequiometria 1:1 favorecido a temperaturas mais baixas com Ka = (1.2 ± 0.2) 104 mol·L-1 a 25 °C e ΔHo = -112 ± 22 kJ·mol-1 e ΔSo = -296 ± 75 J·mol-1·K-1. Conclui-se que para carne, a riboflavina é um fotossensibilizador para oxidação de proteína e não para a descoloração. / The fresh meat pigment oxymyoglobin, MbFe(II)O2, and its oxidized form metmyoglobin, MbFe(III), are both oxidized by riboflavin as photosensitizer. The reaction of MbFe(II)O2 and MbFe(III) with triplet-state riboflavin, 3Rib, involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western-blotting, while the heme iron center is not oxidized. The over-all rate constant for oxidation of MbFe(II)O2 by 3Rib is (3.0 ± 0.5) 109 L·mol-1·s-1 and (3.1 ± 0.4) 109 L·mol-1·s-1 for MbFe(III) in aqueous 0.20 mol·L-1 NaCl phosphate buffer of pH 7.4 at 25 °C as determined by transient absorption laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using single photon counting time resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has Ka = (1.2 ± 0.2) 104 mol·L-1 at 25 °C with ΔHo = -112 ± 22 kJ·mol-1 and ΔSo = -296 ± 75 J·mol-1·K-1. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.