Artificial glycosyl phosphorylases

alpha- and beta-Cyclodextrin 6(A),6(D)-diacids (1 and 2), beta-cyclodextrin-6-monoacid (14), beta-cyclodextrin 6(A),6(D)-di-O-sulfate (16) and beta-cyclodextrin-6-heptasulfate (19) were synthesised. Acids 1, 2 and 14 were made from perbenzylated alpha- or beta-cyclodextrin, by diisobutylaluminum hydride (DIBAL)-promoted debenzylation, oxidation and deprotection. Addition of molecular sieves was found to improve the debenzylation reaction. Sulfates 16 and 19 were made by sulfation of the appropriately partially protected derivatives and deprotection. Catalysis of 4-nitrophenyl glycoside cleavage by these cyclodextrin derivatives was studied. Compounds 1, 2 and 16 were found to catalyse the reaction, with the catalysis following Michaelis-Menten kinetics and depending first order on the phosphate concentration. In a phosphate buffer (0.5 M, 59 degrees C, pH 8.0), K(M) varied from 2-10 mM and the k(cat)/k(uncat) ratio from 80-1000 depending on the stereochemistry of the substrate and the catalyst, with 2 being the best catalyst and with the sulfated 16 also displaying catalytic ability. The monoacid 14 and the heptasulfate 19 were not catalytic.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

Spin-orbit splitting of the copper halides and its volume dependence

We have investigated theoretically and experimentally the dependence of the spin-orbit splitting of the edge excitons in CuCl, CuBr, and CuI on volume. The results indicate a large contribution of the change in p(halogen)-d(Cu) hybridization with volume, especially for CuCl.     

Commutants of nest algebras modulo the compact operators

Any operatorx which commutes modulo the compact operators with a nest algebra is of the form λI+C, where λ is a scalar andC is a compact operator. Any derivation from a nest algebra on a Hilbert spaceH into the compact operators onH is implemented by a compact operator. Any derivation on a quasitriangular operator algebra is inner.     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.     

About the limits of existence of α-cluster structure in nuclei

The shape of the d-α coincidence spectrum from the reaction ¹²C(⁶Li, d)¹⁶O(α)¹²C in the region corresponding to the 20.9 MeV 7^? level in ¹⁶O has been measured. Also, measurements of the α-particle elastic scattering excitation functions on ¹²C and ¹⁶O have been made in the regions corresponding to the α-cluster levels found in the (⁶Li, d) reactions. A comparison of the d-α coincidence spectra and excitation functions allows us to draw conclusions about splitting of the α-cluster states and region of their existence.