PHENOLIC COMPOUNDS RELEASED FROM OAK, CHERRY, CHESTNUT AND

Advantages and drawbacks from the use of oak chips in oenology are well documented; wood oenological value is primarily related to cooperage potential, and not addressed from the oenologist view; for this reason other woods did not had similar attention. Polyphenols release is determinant to recognize the oenological value. Untoasted, light, medium and heavy toasted chips from oak, cherry, robinia and chestnut woods were add, to a model wine solution. Total polyphenolic content using Folin Ciocalteau reagent, absorbance at 280nm, identifi cation and quantifi cation of low molecular weight phenolic compounds were determined. Oak and chestnut released high amounts of phenolic compounds whilst cherry presented different behaviour. Robinia had the poorest performance, regarding low molecular weight phenolic compounds; the high values of absorbance and total polyphenolic found suggest the release of different phenolics. To our knowledge, this is the fi rst study reporting toasting infl uence on the release of phenolic compounds from other kinds of wood species than oak

Coupling constants again: Experimental restraints in structure refinement

Utilization of coupling constants as restraints in computational structure refinement is reviewed. In addition, we address the effect of conformational averaging and examine different approaches to apply the restraints when the experimental observable is obviously a result of averaging. Here, two different computational methods are compared. The simulation of a single structure with time-dependent restraints produces results very similar to those obtained with the calculation of numerous copies of the molecule (an ensemble of structures) and ensemble averaging. The advantages and disadvantages of the two methods are illustrated with simulations of cyclosporin A, for which 117 NOEs and 62 homo- and heteronuclear coupling constants have been measured. © 1994 ESCOM Science Publishers B.V