Recombinant Thaumatin-Like Protein (rTLP) and Chitinase (rCHI) from Vitis vinifera as Models for Wine Haze Formation

Cross-linking net aggregates of thermolabile thaumatin-like proteins (TLPs) and chitinases (CHIs) are the primary source of haze in white wines. Although bentonite fining is still routinely used in winemaking, alternative methods to selectively remove haze proteins without affecting wine organoleptic properties are needed. The availability of pure TLPs and CHIs would facilitate the research for the identification of such technological advances. Therefore, we proposed the usage of recombinant TLP (rTLP) and CHI (rCHI), expressed by Komagataella phaffii, as haze-protein models, since they showed similar characteristics (aggregation potential, melting point, functionality, glycosylation levels and bentonite adsorption) to the native-haze proteins from Vitis vinifera. Hence, rTLP and rCHI can be applied to study haze formation mechanisms on a molecular level and to explore alternative fining methods by screening proteolytic enzymes and ideal adsorptive resins.     

Crystal structures and repair studies reveal the identity and the base-pairing properties of the UV-induced spore photoproduct DNA lesion

UV light is one of the major causes of DNA damage. In spore DNA, due to an unusual packing of the genetic material, a special spore photoproduct lesion (SP lesion) is formed, which is repaired by the enzyme spore photoproduct lyase (Spl), a radical S-adenosylmethionine (SAM) enzyme. We report here the synthesis and DNA incorporation of a DNA SP lesion analogue lacking the phosphodiester backbone. The oligonucleotides were used for repair studies and they were cocrystallized with a polymerase enzyme as a template to clarify the configuration of the SP lesion and to provide information about the base-pairing properties of the lesion. The structural analysis together with repair studies allowed us to clarify the identity of the preferentially repaired lesion diastereoisomer.     

The Relationship between Craze Structure and Molecular Weight in Polystyrene as Revealed by µSAXS Experiments

Summary: The phenomenon of crazing in polymers has received considerable attention in the past as it is thought to play a pivotal role in determining the performance of polymers under load. One aspect of particular interest has been the interconnection between molecular structure, craze characteristics, and macromechanical properties. In the present study, three different grades of polystyrene (PS) with different molecular weights have been systematically investigated in situ with synchrotron radiation microfocus small‐angle X‐ray scattering (µSAXS). The results suggest that there are different mechanisms operating in PS samples with low and very high molecular weights, compared to those of medium‐to‐high molecular weight. Previously it was thought that, above the critical molecular weight of entanglement, the effect of molecular weight on PS's mechanical behaviour at room temperature was negligible.

Craze evolution as a function of strain in PS.     

Synthesis of D-seco-13α-Androst-5-ene Derivatives

Summary. 3β-Hydroxy-16,17-seco-13α-androsta-5,16-dien-17-al was obtained from 3β-acetoxyandrost-5-en-17-one in six steps with a Grob fragmentation as the key step. This seco-steroid, containing a formyl group and an unsaturated side-chain in a sterically favourable cis position, is a useful synthon for the synthesis of novel heterocycles condensed to the 3β-hydroxy-13α-androst-5-en-17-one skeleton.     

Convergence results for multistep Runge-Kutta methods

Summary. Recently Ch. Lubich proved convergence results for Runge-Kutta methods applied to stiff mechanical systems. The present paper discusses the new ideas necessary to extend these results to general linear methods, in particular BDF and multistep Runge-Kutta methods. Received August 9, 1993 / Revised version received May 3, 1994     

Sonochemiluminescence from a single cavitation bubble in water

Single bubble feels the pressure: Sonochemical luminescence has been detected in a single-cavitation bubble within a narrow pressure domain below the sonoluminescence threshold. The parameter space of single-bubble sonochemistry is distinct from that of single-bubble atomic and molecular line emissions.