Reflection of light by a slab containing electrically small dielectric spheres

Theoriginal and theenhanced Maxwell-Garnett estimates for the permittivity of a particulate medium are applied to the reflection of light by a composite dielectric slab. The reflection coefficients for incident s and p polarizations are calculated and some curves are plotted and discussed.     

Metal-Assisted Oxidative Cyclization of Arylamidrazones I. Synthesis of 3-Acetyl-1,4-dihydro-1-phenyl-1,2,4-benzotriazine

In the presence of RuCl₃, N-phenylamidrazone underwent oxidative cyclization into 1,4-dihydro-1-phenyl-1,2,4-benzotriazine, the structure of which is established by spectral and X-ray diffraction data.     

Spectroscopic properties of Carcinus aestuarii hemocyanin and its structural subunits

Hemocyanin (Hc) of Carcinus aestuarii contains three major and one minor electrophoretically separable polypeptide chains which were purified by fast protein liquid chromatography (FPLC) ion exchange chromatography. N-terminal amino acid sequences of four structural subunits (SSs) from C. aestuarii were compared with known N-terminal sequences from other arthropodan hemocyanins. The conformational changes, induced by various treatments, were monitored by far UV, CD and fluorescence spectroscopy. The critical temperatures for the structural subunits, Tc, determined by fluorescence spectroscopy, are in the region of 52-59 degrees C and coincide with the melting temperatures, Tm (49-55 degrees C), determined by CD spectroscopy. The free energy of stabilization in water, delta GDH2O, toward guanidinium hydrochloride is about 1.3 times higher for the dodecameric Hc as compared to the isolated subunits and about one time higher for Cal, comparing with other SSs. The studies reveal that the conformational stability of the native dodecamer towards various denaturants (temperature and guanidinium hydrochloride) indicate that the quaternary structure is stabilized by oligomerization between structural subunits, and the possibility of a structural role of the sugar mojeties cannot be excluded.     

Synthesis of some dibenzodiazepinone derivatives as potent and m2-selective antimuscarinic compounds

Two series of 5-[[4-[4-(dialkylamino)butyl]-l-cyclohexyl]acetyl], and 5-[(dialkylamino)acyl]-10,11-dihydro-5H- dibenzo[b,e][1,4]diazepin-11-ones were synthesized as potential m2-selective ligands 1,2. Their affinity and selectivity for the muscarinic cholinergic receptor m-AChR subtypes were determined. Replacing a nitrogen with CH in the piperidine ring of 5-[[4-[4-(dialkylamino)butyl]-l-piperidinyl]acetyl]-10,11-dihydro-5H-dibenzo-[b,e][1,4]diazepin-11-ones 3 significantly altered the affinity and selectivity to the muscarinic receptor subtypes.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazines

Summary.  A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-e][1,2,4]triazines

A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Chemical Biological Sensors Based on Advances in Conducting Electroactive Polymers

Advances in conducting electroactive polymers (CEPs) have driven the design of novel chemical and biochemical sensors. The redox properties of CEPs have been intensely studied for more than two decades with emphasis on their synthesis and characterization. Little attention has been paid to the importance of mechanism in sensor designs. However, in order to design robust and stable sensors, it is important to understand how the polymer structure, morphology, adhesion properties and microenvironment affect sensor performance. This work describes how chemical and biological sensors have been designed, fabricated, characterized and tested based on the fundamental understanding in CEPs. The use of photopolymerized conducting polymers in sensor designs is described. Four focus areas are presented in which the electronic properties of CEPs have enabled the design of novel sensors for organics, nucleic acids, biological molecules, vapors and metal ions.     

A novel Cu,Zn superoxide dismutase from the fungal strain Humicola lutea 110: isolation and physico-chemical characterization

The fungal strain Humicola lutea 110 produces a mangan- and a copper zinc-containing superoxide dismutases (SOD). In this study, the purification, N-terminal sequence and spectroscopic properties of the new Cu,Zn SOD are described. The preparation of the pure metalloenzyme was achieved via treatment of the strain with acetone followed by gel and ion exchange chromatography. The protein consists of 302 amino acid residues and has a molecular mass of approximately 32 kDa, as determined by PAG electrophoresis and 3100 U mg-1 protein-specific activity. It is a dimeric enzyme with two identical subunits of 15,950 Da, as indicated by SDS-PAGE, mass spectroscopic and amino acid analysis. The N-terminal sequence analysis of the Cu,Zn SOD from the fungal strain revealed a high degree of structural homology with enzymes from other eukaryotic sources. Conformational stability and reversibility of unfolding of the dimeric enzyme were determined by fluorescence and circular dichroism (CD) spectroscopy. The critical temperature of deviation from linearity (Tc) of the Arrhenius plot ln (Q-1(-1)) vs. 1/T was calculated to be 68 degrees C and the respective activation energy for the thermal deactivation of the excited indole chromophores is 42 kcal mol-1. The melting temperatures (Tm) were determined by CD measurements to be 69 degrees C for the holo- and 61 degrees C for the apo-enzyme. The fluorescence emission of the Cu,Zn SOD is dominated by 'buried' tryptophyl chromophores. Removal of the copper-dioxygen system from the active site caused a 4-fold increase of the fluorescence quantum yield and a 10 nm shift of the emission maximum position towards higher wavelength.