Laser-induced temperature jump electrochemistry on gold nanoparticle-coated electrodes

Laser-induced temperature jumps (LITJs) at gold nanoparticle-coated indium tin oxide (ITO) electrodes in contact with electrolyte solutions have been measured using temperature-sensitive redox probes and an infrared charge-coupled device. Upon irradiation with 532 nm light, interfacial temperature changes of ca. 20 degrees C were recorded for particle coverages of ca. 1 x 1010 cm-2. In the presence of a redox molecule, LITJ yields open-circuit photovoltages and photocurrents that are proportional to the number of particles on the surface. When ssDNA was used to chemisorb nanoparticles to the ITO surface, solution concentrations as low as 100 fM of target ssDNA-modified nanoparticles could be detected at the electrode surface.     

Rapid two-step synthesis of mitrin from heparosan: a replacement for heparin

We have engineered a two-step enzymatic synthesis of Mitrin which is a more potent and homogeneous anticoagulant than the current animal-derived heparin. This engineered heparin may have advantages of being free from animal-derived pathogens and may also have reduced side effects such as heparin induced thrombocytopenia. This approach can also be extended to tailor heparin-based drugs with improved therapeutic characteristics to treat other disorders or infections in which heparin-like molecules play a major role.     

Reversal of diastereoselectivities in intra- and intermolecular reactions of 2-adamantanylidenes primarily caused by electron-donating and electron- withdrawing substituents on C5

[reaction: see text] A reversal of diastereoselectivity was observed for novel 5-(trimethylsilyl)adamantan-2-ylidene (1c) with regard to 5-hydroxyadamantan-2-ylidene (1a). Ostensibly in intermolecular reactions, 5-substituted 2-adamantanylidenes (1) are sterically unbiased. However, inductive effects originating from the pendant group bend the divalent carbon bridge of 1 either toward (ERG's, e.g., -Si(CH(3))(3)) or away from (EWG's, e.g., -OH) the gamma-position. Hence, the more exposed side is more susceptible to intermolecular reaction and the other side concomitantly undergoes intramolecular 1,3-CH insertions more readily.     

Studies on high-temperature amination reactions of aromatic chlorides using discrete Palladium-N-Heterocyclic Carbene (NHC) complexes and in situ palladium/imidazolium salt protocols

The palladium catalysed coupling of aryl chlorides and amines can be readily achieved with short reaction times when carried out at high temperatures under thermal or microwave conditions. These coupling protocols are successful using two co-ordinate palladium-N-heterocyclic carbene complexes, or imidazolium salt protocols.     

Directed flow of lambda hyperons in (2-6 )A GeV Au+Au collisions

Directed flow measurements for Lambda hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2A, 4A, and 6A GeV; b<5-6 fm). The measurements indicate that Lambda hyperons flow consistently in the same direction but with smaller magnitudes. A strong positive flow [for Lambdas] has been predicted in calculations which include the influence of the Lambda-nucleon potential. The experimental flow ratio Lambda/p is in qualitative agreement with expectations (approximately 2/3) from the quark counting rule at 2A GeV but is found to decrease with increasing beam energy.     

Distance in stratified graphs

A graph G is stratified if its vertex set is partitioned into classes, called strata. If there are k strata, then G is k-stratified. These graphs were introduced to study problems in VLSI design. The strata in a stratified graph are also referred to as color classes. For a color X in a stratified graph G, the X-eccentricity e _X(v) of a vertex v of G is the distance between v and an X-colored vertex furthest from v. The minimum X-eccentricity among the vertices of G is the X-radius rad_X G of G and the maximum X-eccentricity is the X-diameter diam_X G. It is shown that for every three positive integers a, b and k with ab, there exist a k-stratified graph G with rad_X G = a and diam_X G = b. The number s _X denotes the minimum X-eccetricity among the X-colored vertices of G. It is shown that for every integer t with rad_X G t diam_X G, there exist at least one vertex v with e _X(v) = t; while if rad_X G t s _X, then there are at least two such vertices. The X-center C _X(G) is the subgraph induced by those vertices v with e _X(v) = rad_X G and the X-periphery P _X (G) is the subgraph induced by those vertices v with e _X(G) = diam_X G. It is shown that for k-stratified graphs H ₁, H ₂,..., H _k with colors X ₁, X ₂,..., X _k and a positive integer n, there exists a k-stratified graph G such that C X _i(G) H _i (1 ; i ; k1) and for i j. Those k-stratified graphs that are peripheries of k-stratified graphs are characterized. Other distance-related topics in stratified graphs are also discussed.     

Triazine Dendrimers for Drug Delivery: Evaluation of Solubilization Properties,Activity in Cell Culture,and In Vivo Toxicity of a Candidate Vehicle

Three criteria are evaluated to assess the potential of a dendrimer based on triazines, 1, for use as a vehicle for drug delivery. These criteria are: (1) its ability to solubilize small hydrophobic guests as measured spectrophotometrically; (2) its ability to deliver a drug in vitro as evaluated using a gene reporter assay; and (3) its in vivo toxicity in mice as determined by autopsy and screens of liver and kidney function. Vehicle 1 solubilizes pyrene to a similar extent to dendrimers based on poly(arylether)s, 4, encapsulating approximately 0.2 molecules of pyrene per dendrimer. This activity is approximately 10-fold greater than that of the more polar poly(propyleneimine) and poly(amidoamine) dendrimers, 2 and 3. Gas-phase computational models reveal that both 1 and 4 have cores that are accessible to solvent, suggesting that these dendrimers can occupy much greater volumes than 2 and 3 whose cores are confined toward the interior of the structure. Electrostatic potential maps can be used to rationalize differences in solubilization between 1 and 4. Precipitation results from mixing cationic 1 with the anionic indomethacin, but not with methotrexate, suggesting that the composition of the drug may dictate the scope of delivery applications. Dendrimer 1 solubilizes 10-hydroxycamptothecin and a novel bisindolemethane; approximately four and five molecules of drug per dendrimer are solubilized, respectively. In cell-culture experiments using a luciferase reporter gene assay, the dendrimer:bisindolemethane conjugate shows comparable activity to the bisindolemethane delivered in aqueous DMSO, suggesting that the dendrimer does not preclude delivery of the molecule to an intracellular target. Preliminary toxicology studies of 1 in mice show that this molecule has no adverse toxicity to the kidneys or the liver in single doses delivered intraperitoneally up to 10?mg/kg.