Steroid oxidoreductase activity of alcohol dehydrogenases from horse, rat, and human liver.

Alcohol dehydrogenase from horse (isoenzyme SS and ES, but not EE), rat and human liver were found to catalyze the NAD-dependent oxidation of 3beta-hydroxy groups in 5alpha- and 5beta-steroids of the C19, C21, and C24 series. The enzymes from horse and rat liver were more active on 5beta-than on 5alpha-steroids. This difference was most marked with the enzyme from rat liver, especially with 3beta-hydroxyandrostan-17-ones and 3beta-hydroxypregnan-20-ones as substrates. The Km of isoenzyme ES from horse liver was lower for 3beta-hydroxy-5alpha-cholanoic acid (0.4 muM) than for 3beta-hydroxy-5beta-cholanoic acid (0.9 muM). 3alpha-Hydroxysteroids were not substrates for the enzymes from horse and rat liver. Human liver alcohol dehydrogenase had low affinity for 3beta-hydroxy-5alpha (and 5beta)-cholanoic acids, but oxidation could be clearly demonstrated by gas chromatographic analysis of the products.     

Photochemical and photophysical properties of a poly(propylene amine) dendrimer functionalized with E-stilbene units

A second generation poly(propylene amine) dendrimer functionalized at the periphery with eight E-stilbene and eight 4-tert-butylbenzenesulfonyl units has been prepared. The absorption spectrum, fluorescence spectrum and decay, E<==>Z photoisomerization, and photocyclization of the Z-isomer of the stilbene units have been investigated in air equilibrated acetonitrile solutions. For comparison purposes, a reference compound of the peripheral dendrimer units, namely 4-tert-butyl-N-propyl-N-(4-styryl-benzyl)-benzenesulfonamide, has also been studied. The quantum yield of the E-->Z photoisomerization reaction (0.30) and the fluorescence quantum yield of the E isomer (0.014) are substantially smaller for the units appended to the dendrimer compared to those of the reference compound (0.50 and 0.046, respectively). The presence of a red tail and the biexponential decay of the emission band of the dendrimer indicate formation of excimers between the stilbene units appended at the poly(propylene amine) dendritic structure. Under the experimental conditions used (lambda(exc)= 313 nm), a Z/E photostationary state (around 9 : 1 for both reference compound and dendrimer ) is reached in the time scale of minutes. On continuing irradiation, other photoreactions take place in the time scale of hours: the stilbene moiety of compound undergoes photocyclization to phenanthrene (quantum yield 0.015), whereas in dendrimer photocyclization to phenanthrene is accompanied by other processes, including a photoreaction involving the internal amine groups.     

Medical Image Authentication Method Based on the Wavelet Packet and Energy Entropy

The transmission of digital medical information is affected by data compression, noise, scaling, labeling, and other factors. At the same time, medical data may be illegally copied and maliciously tampered with without authorization. Therefore, the copyright protection and integrity authentication of medical information are worthy of attention. In this paper, based on the wavelet packet and energy entropy, a new method of medical image authentication is designed. The proposed method uses the sliding window to measure the energy of the detail information. In the time–frequency data distribution, the local details of the data are mined. The complexity of energy is quantitatively described to highlight the valuable information. Based on the energy weight, the local energy entropy is constructed and normalized. The adjusted entropy value is used as the feature vector of the authentication information. A series of experiments show that the authentication method has good robustness against shearing attacks, median filtering, contrast enhancement, brightness enhancement, salt-and-pepper noise, Gaussian noise, multiplicative noise, image rotation, scaling attacks, sharpening, JPEG compression, and other attacks.