Invariant distribution on strange attractors in highly dissipative systems

We obtain analytically by an iterative procedure the equilibrium invariant distribution for a class of strange attractors in highly dissipative systems. The zeroth order distribution is found by solving the phase-averaged Markov equation. Repeated iterations over the map yield the higher order distributions that reveal successively finer structures. The analytical results have been compared quantitatively to numerical results for the Zaslavskii map.     

Equilibria in complexes of n-heterocyclic compounds—LI. Synergic solubility and x-ray crystal structure analysis of mer-chloro-oxalato-tris-pyridine-iridium(III), [IrCl(py)3(C2O4)]

The title compound, mer-[IrCl(py)₃(C₂O₄)], has been made by the reaction of the known trans-dichloro-tetrapyridine-iridium(III) chloride with ethanedioate ion(oxalate) in aqueous ethanol. A non-electrolyte, it resembles its rhodium eutrope in showing extraordinary synergic solubility in water: pyridine. An X-ray structure determination has confirmed the mer geometry.     

Pressurized membrane indicator system for fluorogenic-based fiber-optic chemical sensors

A new kind of fiber-optic-based chemical sensor for the detection of chemical species in solution is described. The sensor uses a fluorogenic indicator that is forced through an ultrafiltration membrane into the analyte solution. Complex formation between the indicator molecule and target ion occurs at the membrane/solution interface, where light from a bifurcated fiber-optic cable stimulates fluorescence. Fluorescence emission from the sample is transmitted back up the cable to a photodiode detector. Characterization of the sensor was performed using the response of the indicator, 8-hydroxyquinoline-5-sulfonic acid, to magnesium ion. The sensor responds linearly to increasing and decreasing concentration changes on time scales of 1 s. Chemical modification of the indicator solution to enhance sensitivity is demonstrated. The use of an internal standard to correct for variations in indicator flow-rate and pressure is discussed.     

Detection of volatile organic compounds using surface enhanced Raman spectroscopy substrates mounted on a thermoelectric cooler

Preliminary results for a volatile organic compound (VOC) sensor based on surface enhanced Raman spectroscopy (SERS) are described. The sensor is comprised of a SERS substrate mounted on a thermoelectric cooler (TEC). The SERS substrate is chemically modified with a thiol coating that prevents oxidation of the roughened silver surface and attracts the analyte of interest to the SERS surface. Using this sensor, detection of chlorinated solvents, aromatic compounds, and methyl t-butyl ether (MTBE) is demonstrated.     

Growth control by cell to cell contact.

Control of cell growth by cell to cell contact is reviewed with particular emphasis on two systems--contact inhibition of growth observed with Swiss 3T3 cells and the mitogenic stimulation of Schwann cells by dorsal root ganglia neurites. In both cases the biological effect can be reproduced by the addition of surface membranes to the corresponding cells. In the case of contact inhibition of 3T3 cells, biological activity appears to correlate with membrane binding to the cells. An octylglucoside extract of 3T3 plasma membranes retains the biological activity (growth inhibition) of the original membranes.     

Porphyrins XXXV . Exciton coupling in μ-oxo Scandum dimers

The absorption and emission spectra at room temperature and at 77 K are reported for the monomers and μ-oxo dimers of (OEP)Sc(III) and (TPP)Sc(III). [Here (OEP) is octaethylporphin and (TPP) is tetraphenylporphin.] Exciton coupling effects are strongest in the B(Soret) band of [(OEP)Sc]₂O dimer: (i) The peak is blue shifted by 11 nm; (ii) the Soret band has a long red tail out to 480 mn; (iii) the fluorescence polarization shows a broad negativ band ≈ 440 nm. A vibronic exciton coupling model can roughly interpret the data if there is substantial and variable tilting of the ring planes. Exciton effects are weaker in the B(Soret) band of [(TPP)SC]₂O, presumably because there is less tilting. The effect of dimer formation on the Q band of [(OEP)Scl₂O is to red shift the band ≈ 420 cm^?1 and to nearly double the Q(0,0) halfwidth; there is no change in fluorescence yield with dimerization. Presumably for Q bands exciton coupling is weaker than inhomogeneous broadening. Both the phosphorescence yield and triplet lifetime at 77 K drop by $\text{case2}\text{3}$ in the dimer, showing faster radiationless decay.     

Detection of ligand binding hot spots on protein surfaces via fragment-based methods: application to DJ-1 and glucocerebrosidase

The identification of hot spots, i.e., binding regions that contribute substantially to the free energy of ligand binding, is a critical step for structure-based drug design. Here we present the application of two fragment-based methods to the detection of hot spots for DJ-1 and glucocerebrosidase (GCase), targets for the development of therapeutics for Parkinson’s and Gaucher’s diseases, respectively. While the structures of these two proteins are known, binding information is lacking. In this study we employ the experimental multiple solvent crystal structures (MSCS) method and computational fragment mapping (FTMap) to identify regions suitable for the development of pharmacological chaperones for DJ-1 and GCase. Comparison of data derived via MSCS and FTMap also shows that FTMap, a computational method for the identification of fragment binding hot spots, is an accurate and robust alternative to the performance of expensive and difficult crystallographic experiments.