Substrate electric dipole moment exerts a pH-dependent effect on electron transfer in Escherichia coli photolyase

Transient absorption spectroscopy is used to demonstrate that the electric dipole moment of the substrate cyclobutane thymine dimer affects the charge recombination reaction between fully reduced flavin adenine dinucleotide (FADH-) and the neutral radical tryptophan 306 (Trp306*) in Escherichia coli DNA photolyase. At pH 7.4, the charge recombination is slowed by a factor of 1.75 in the presence of substrate, but not at pH 5.4. Photolyase does bind substrate at pH 5.4, and it seems that this pH effect originates from the conversion of FADH- to FADH2 at lower pH. The free-energy changes calculated from the electric field parameters and from the change in electron transfer rate are in good agreement and support the idea that the substrate electric dipole is responsible for the observed change in electron transfer rate. It is expected that the substrate electric field will also modify the physiologically important from excited 1FADH- to the substrate in the DNA repair reaction.     

The decomposition numbers of the hecke algebra of typeF 4

LetW be the finite Coxeter group of typeF ₄, andH _r (q) be the associated Hecke algebra, with parameter a prime powerq, defined over a valuation ringR in a large enough extension field ofQ, with residue class field of characteristicr. In this paper, ther-modular decomposition numbers ofH _R (q) are determined for allq andr such thatr does not divideq. The methods of the proofs involve the study of the generic Hecke algebra of typeF ₄ over the ringA = ℤ[u ^1/2,u ^-1/2] of Laurent polynomials in an indeterminateu ^1/2 and its specializations onto the ring of integers in various cyclotomic number fields. Substancial use of computers and computer program systems (GAP, MAPLE, Meat-Axe) has been made.     

Contributions of the 8-methyl group to the vibrational normal modes of flavin mononucleotide and its 5-methyl semiquinone radical

Resonance Raman spectroscopy is a powerful tool to investigate flavins and flavoproteins, and a good understanding of the flavin vibrational normal modes is essential for the interpretation of the Raman spectra. Isotopic labeling is the most effective tool for the assignment of vibrational normal modes, but such studies have been limited to labeling of rings II and III of the flavin isoalloxazine ring. In this paper, we report the resonance and pre-resonance Raman spectra of flavin mononucleotide (FMN) and its N5-methyl neutral radical semiquinone (5-CH 3FMN(*)), of which the 8-methyl group of ring I has been deuterated. The experiments indicate that the Raman bands in the low-frequency region are the most sensitive to 8-methyl deuteration. Density functional theory (DFT) calculations have been performed on lumiflavin to predict the isotope shifts, which are used to assign the calculated normal modes to the Raman bands of FMN. A first assignment of the low-frequency Raman bands on the basis of isotope shifts is proposed. Partial deuteration of the 8-methyl group reveals that the changes in the Raman spectra do not always occur gradually. These observations are reproduced by the DFT calculations, which provide detailed insight into the underlying modifications of the normal modes that are responsible for the changes in the Raman spectra. Two types of isotopic shift patterns are observed: either the frequency of the normal mode but not its composition changes or the composition of the normal mode changes, which then appears at a new frequency. The DFT calculations also reveal that the effect of H/D-exchange in the 8-methyl group on the composition of the vibrational normal modes is affected by the position of the exchanged hydrogen, i.e., whether it is in or out of the isoalloxazine plane.     

Constraint Programming Based Lagrangian Relaxation for the Automatic Recording Problem

Whereas CP methods are strong with respect to the detection of local infeasibilities, OR approaches have powerful optimization abilities that ground on tight global bounds on the objective. An integration of propagation ideas from CP and Lagrangian relaxation techniques from OR combines the merits of both approaches. We introduce a general way of how linear optimization constraints can strengthen their propagation abilities via Lagrangian relaxation. The method is evaluated on a set of benchmark problems stemming from a multimedia application. The experiments show the superiority of the combined method compared with a pure OR approach and an algorithm based on two independent optimization constraints.