As a model for riboflavin, lumiflavin was investigated using density functional theory methods (B3LYP/6-31G* and B3LYP/6-31+G**) with regard to the proposed cascade of intermediates formed after excitation to the triplet state, followed by electron-transfer, proton-transfer, and radical[bond]radical coupling reactions. The excited triplet state of the flavin is predicted to be 42 kcal/mol higher in energy than the singlet ground state, and the pi radical anion lies 45.1 kcal/mol lower in energy than the ground-state flavin and a free electron in the gas phase. The former value compares to a solution-phase triplet energy of 49.8 kcal/mol of riboflavin. For the radical anion, the thermodynamically favored position to accept a proton on the flavin ring system is at N(5). A natural population analysis also provided spin density information for the radicals and insight into the origin of the relative stabilities of the six different calculated hydroflavin radicals. The resulting 5H-LF* radical can then undergo radical[bond]radical coupling reactions, with the most thermodynamically stable adduct being formed at C(4'). Vibrational spectra were also calculated for the transient species. Experimental time-resolved infrared spectroscopic data obtained using riboflavin tetraacetate are in excellent agreement with the calculated spectra for the triplet flavin, the radical anion, and the most stable hydroflavin radical.

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A survey was conducted of four-year institutions that teach undergraduate organic chemistry laboratories in the United States. The data include results from over 130 schools, describes the current practices at these institutions, and discusses the statistical results such as the scale of the laboratories performed, the chemical techniques applied, the instrumentation available, the laboratory equipment used, the chemistry topics covered, the way chemical safety is presented, and how chemical waste is handled. These results provide a "snapshot" of the current state of the undergraduate organic teaching laboratory.

We are developing a technology based on the combined application of riboflavin (RB) and light for inactivating pathogens in blood products while retaining the biological functions of the treated cells and proteins. Virus and bacteria reduction measured by tissue culture infectivity or colony formation with UV light alone and in combination with RB yield equivalent results. The effects of RB as a sensitizing agent on DNA in white cells, bacteria and viruses in combination with UV light exposure have been evaluated. UV-mediated DNA degradation in Jurkat T cells and leukocytes in plasma as measured by the FlowTACS assay was significantly increased in the presence of RB. Agarose gel electrophoretic analysis of DNA in Escherichia coli and leukocytes in plasma demonstrated enhanced DNA degradation in the presence of RB. UV light in combination with RB prevented the reactivation of lambda phage compared with samples irradiated in the absence of RB. UV-mediated oxidative damage in calf thymus DNA was also enhanced in the presence of RB. These observations clearly demonstrate that the presence of RB and UV light selectively enhances damage to the guanine bases in DNA. These data also suggest that the type and extent of damage to DNA for virus in the presence of RB and light make it less likely to be repaired by normal repair pathways available in host cells.

The photoreaction between riboflavin tetraacetate and nucleosides was investigated using time-resolved infrared spectroscopy (TRIR), laser flash photolysis with UV−vis detection, fluorescence quenching, absorption spectroscopy, and density functional theory calculations. Riboflavin tetraacetate (RBTA) was studied experimentally with indole and with Sheu and Foote's organic soluble silylated guanosine (G‘). Lumiflavin and (R)-2-amino-(S)-4-hydroxy-(R)-5-(hydroxymethyl)-tetrahydrofuran were used as computational models for RBTA and for the sugar moiety of the nucleoside, respectively, using density functional theory calculations (B3LYP/6-31G* and B3LYP/6-31+G**). Vibrational spectra were also calculated for the transient species. Time-resolved infrared spectroscopic data obtained using RBTA are in excellent agreement with the calculated spectra for the triplet flavin, and in the presence of silylated guanosine, with the formation of the most stable hydroflavin radical, RBTH, by an electron transfer−proton transfer mechanism. Although the gas-phase calculations indicate that abstraction of a hydrogen atom from the sugar is slightly exothermic, this reaction does not proceed at a rate measurable as monitored by TRIR spectroscopy. Singlet RBTA is also quenched by G‘ in methylene chloride. Stern−Volmer analysis of the fluorescence quenching data indicates that this reaction proceeds with a rate constant of 8.7 × 108 M-1 s-1.