The principal purpose of the present study was to prove the existence of the weak interaction between the halogenoid iodine monochloride and the condensed polycyclic aromatic hydrocarbons, phenanthrene, anthracene pyrene, chrysene, and benzanthracene (see Figure 1).

Kinetic studies, as well as the thermodynamics of the formation of the Cu(II)-Pyridine-2-azo-p-dimethylaniline complex ion in aqueous solutions, and in the presence of sodium dodecyl sulfate (SDS) are reported. The kinetic determinations of the formation of complex were performed using the temperature jump technique. The rate constants in the forward (k$\rm \sb{f}$) and backward (k$\rm\sb{b}$) directions had values of (2.10 $\pm$ 0.97) $\times\ 10\sp7$ scM$\rm \sp{-1}s\sp{-1}$ and (10.0 $\pm$ 0.35) $\rm \times\ 10\sp{2}\ \sb{s}\sp{-1}$ respectively in aqueous solution at 25$\sp\circ$C. The numerical values of the rate constants were analyzed satisfactorily according to the Eigen-Wilkins mechanism. The rate of the reaction was determined at different concentrations of SDS. Different effects on the rate of the reaction were observed as the concentration of SDS was changed. The rate of the reaction was enhanced as the concentration of SDS was increased, reaching a maximum at the critical micelle concentration (4.30 $\times$ 10$\sp{-3}$ M SDS), and decreasing slowly as the concentration of SDS became larger than the c.m.c. The kinetic results above the critical micelle concentration were successfully interpreted in terms of the Berezin model. These results indicate that the enhancement observed at the c.m.c. is due to a concentrative effect. The rate coefficient k$\rm \sb{f}$ and k$\rm \sb{b}$ were calculated at two concentrations of SDS. The forward rates of reaction obtained at 25$\sp\circ$C in the presence of SDS are: (3.13 $\pm$ 0.32) $\rm \times\ 10\sp7 M\sp{-1}s\sp{-1}$ at 4.30 $\times$ 10$\sp{-3}$ M SDS and (2.65 $\pm$ 0.21) $\rm \times\ 10\sp7 M\sp{-1}s\sp{-1}$ at 8.82 $\times$ 10$\sp{-3}$ M SDS. The activation enthalpy and entropy for the reaction were also determined at different concentrations of SDS. Both activation parameters showed a minimum at the c.m.c. of the surfactant with a corresponding maximum in the experimental $\rm k\sb{obs}$. Additives such as methyl sulfate and dodecyltrimethylammonium bromide showed no enhancement of the rate of reaction.

Electrocapillary equation for an ideal polarized electrode based on Gibb's adsorption equation is appropriately recast into experimentally measurable quantities in order to apply it to a reversible charge transfer electrode. To calculate the various parameters of the equation developed, experimental details were worked out. For the measurement of Current-time relationship of a single drop, a fast response potentiostat was built by using transistorized chopped stabilized operational amplifiers and precision components in the circuitry with proper compensation for IR-drop in the cell and the electrical double layer capacity. The analysis of I-t curves was done by taking into account the composite nature of the process involved; faradaic and non-faradaic. V(III)/V(II) reversible change transfer electrode in absence of an complexing agent was used for its complete reversibility and high cationic adsorption on the electrode. V(III) and V(II) were prepared in situ in equivalent amounts, by the electrolytic reduction of V(IV). The V(IV) concentration was controlled by photometric titration against standardized potassium permanagate solution. The drop time was taken as a measure of interfacial tension, γ , and electrocapillary curves for the pure solvent... [see PDF file for the rest of the abstract including mathematical figures and equations].

Unambiguous structure assignment of standards is essential for metabolome characterization of infected plants. Complete structure elucidation of eleven natural polyphenols, resveratrol (1), (-)-epicatechin (2), pelargonidin chloride (3), cyanidin chloride (4), cyanin chloride (5), keracyanin chloride (6), caftaric acid (7), quinic acid (8), procyanidin B1 (9), procyanidin B2 (10), and procyanidin C1 (11) by 1H-, 13C, COSY-, TOCSY-, ROESY-, and HMBC-NMR is described. The sinusoidal modulation frequency of 1H-13C-cross-peaks (J-HMBC) was fitted iteratively to sin(πJH,Ctvar) and yielded 2,3J-coupling values for 1H-13C-correlations in the natural polyphenols. Satisfactory fit to standard Karplus-equations was achieved for glycosides directly attached to the aromatic core in cyanin chloride. Molecular dynamics simulation data in vacuum at the AM1-level of theory were shown to approximate the NMR-solution data reasonably well. Analysis of these standards enables the characterization of unknown plant metabolites produced by bacterially stressed Thompson grape plants provided by the USDA. Initial steps for structure elucidation of 72 unknown fractions is discussed. In addition, selective HCl-catalyzed H/D-exchange was observed for aromatic protons H6 and H8 in flavonoid structures containing a 5,7-meta-disubstituted chromelynium core with free OH-groups. The exchange took place readily in compounds 3, 4, and 6, whereas 1, 2, and 5 did not exchange.

Tryptases are trypsin-like enzymes found in mast cell granules. Although in vivo substrates have not been positively identified, tryptases cleave a limited number of potential physiological substrates in vitro, including high molecular weight kininogen (HMWK) and vasoactive intestinal peptide (VIP). Purified human lung mast cell tryptase (HLT) apparently exists as a tetramer with an M$\sb{\rm r}$ of 135-144 kDa by gel filtration, whereas SDS-PAGE yielded two bands of M$\sb{\rm r}$ 29 Kda and 33 Kda. Tryptases are resistant to inhibition by most natural trypsin inhibitors and display some affinity for heparin. The existence of tryptase isozymes has been implied from the cloning of two tryptase cDNAs from human lung tissue, but distinct isozymes have not been isolated and characterized. This knowledge gap has been filled by isolating and characterizing two electrophoretically different forms of human lung mast cell tryptase, designated high-HLT (high molecular weight HLT) and low-HLT (low molecular weight HLT). These two forms of HLT have been separated by chromatography on a cellulose phosphate column, with the high M$\sb{\rm r}$ form eluting with 10 $\mu$M heparin and the low M$\sb{\rm r}$ form subsequently eluting with 1 M NaCl. Using HMWK and VIP as substrates, these two forms of HLT were found to differ with regard to specificity and rate of cleavage. High-HLT initially cleaved HMWK at a single Arg residue, whereas low-HLT cleaved HMWK simultaneously at multiple sites. Both isozymes cleaved VIP at multiple sites, but differed with regard to the preferential site of cleavage. Low-HLT was, on an active site basis, 25 and 2 times more active than high-HLT on HMWK and VIP, respectively. In addition, gel filtration of the isozymes yielded M$\sb{\rm r}$s of 125 Kda for high-HLT and 28 kDa for low-HLT, indicating tetrameric and monomeric quaternary structures, respectively. Both isozymes were inhibited by human secretory leukocyte proteinase inhibitor (SLPI), but not by other trypsin inhibitors tested. This work provides the first evidence for the existence of distinct tryptase isozymes, with supposedly different in vivo functions, and identification of an inhibitor that may control tryptase activity in vivo.

Nitrogen dioxide (NO$\sb2$), an air pollutant produced by burning fossil fuels and a component of cigarette smoke, is thought to contribute to the pathogenesis of pulmonary diseases, such as emphysema. To gain information on the mechanism by which NO$\sb2$ damages the lung, in vitro exposures of $\alpha\sb1$-proteinase inhibitor ($\alpha\sb1$-PI), elastin, bovine serum albumin (BSA), human serum albumin (HSA) and synthetic poly-L-lysine were performed. A genetic deficiency of $\alpha\sb1$-PI predisposes humans to emphysema and NO$\sb2$ has been hypothesized to damage $\alpha\sb1$-PI, which would leave proteases such as human neutrophil elastase, (HNE) free to attack lung structural proteins. The ability of $\alpha\sb1$-PI to inhibit HNE declined with exposure to 50% of the control value at molar ratios of NO$\sb2$:$\alpha\sb1$-PI of 400:1 and greater. Exposure of $\alpha\sb1$-PI to NO$\sb2$ resulted in a 50% loss of immunoreactivity with either monoclonal or polyclonal antibodies in an enzyme-linked immunosorbent assay at molar ratios of NO$\sb2$:$\alpha\sb1$-PI of essentially 100:1 and greater. The mechanisms of these effects were investigated via ultraviolet-visible spectroscopy and amino acid analysis. The remaining target molecules were labeled by reductive methylation of amino groups with $\sp3$H-HCHO prior to treatment with NO$\sb2$ in aqueous solutions at physiological pH. Time course exposure of 5 mg $\sp3$H-insoluble bovine ligamentum nuchae elastin suspensions with up to 120 $\mu$moles of NO$\sb2$ resulted in 90% solubilization of the label. Amino acid analysis of the soluble and insoluble fractions from these exposures confirmed that 80% of the $\sp3$H-dimethyllysine residues were in the soluble fraction. Since these results suggested a specific reactivity of NO$\sb2$ with lysine residues, 400 $\mu$g $\sp3$H-poly-L-lysine was exposed to 120 $\mu$moles NO$\sb2$. Gel filtration chromatography revealed that the 50,000 M$\sb{\rm r}$ $\sp3$H-poly-L-lysine had been degraded to small peptides of 1-3,000 M$\sb{\rm r}$. Similar exposures were conducted using $\sp3$H-BSA and $\sp3$H-HSA, followed by gel filtration chromatography and SDS-PAGE with fluorography. The results suggest that NO$\sb2$ preferentially reacts with Lys-Lys or other specific sequences, resulting in peptide bond cleavage. Under the conditions used, 23% of the BSA tyrosine residues were nitrated and aggregates of HSA indicative of bityrosine cross-link formation were observed. These findings are the first indication that NO$\sb2$ can cause protein fragmentation and provide additional data on the potential of NO$\sb2$ to damage lung proteins, such as elastin.

A novel 0.6 kb LINE family in human DNA, designated L2Hs, has been described (Musich and Dykes 1986). Studies employing clone N6.4, containing three 0.6 kb segments of this family, indicate that these sequences are interspersed and moderately repetitive. Two additional variant sequences of the L2Hs family, N6.1 and N6.3, have been identified. Restriction mapping of each cloned segment indicates similarities among N6.4, N6.3 and N6.1. When the cloned DNAs were cleaved with restriction enzymes and subjected to cross-hybridization, each cloned insert produced a pattern indicating that the sequences contained in N6.1 and N6.3 are represented in at least one of the three 0.6 kb segments within the clone N6.4. Hybridization of human genomic DNA digested with KpnI or KpnI+AccI reveals differences in nuclear organization for these segments. For any particular human DNA, the hybridization patterns for each of the three probes overlap. However, these differences indicate that the inserts in N6.1 and N6.3 and one of the N6.4 inserts each represents a subset of the L2Hs LINE family. Sequence analysis of N6.1 indicates that the probability of a functional translation product from N6.1 transcript is not high. The sequence contains stop and nonsense codons in all reading frames. However, the DNA has properties suggesting a structural, non-coding role. The N6.1 sequence contains 11 regions of alternating purine and pyrimidines which can affect the three dimensional structure and, therefore, the structural behavior of the molecule. In addition, putative binding regions for microtubule-associated proteins have been identified. A cloned variant of the XbaI family of repetitive DNAs, PuHu7, was identified. Studies of its genomic organization showed a tandem arrangement similar to other, previously described members of this family. The genomic organization of a previously undescribed repetitive DNA family is also reported. This family descriptor is the clone PuHu26. Hybridization of genomic DNA digested with HindIII showed that sequences homologous to PuHu26 are tandemly organized. Genomic DNA cleaved with EcoRI revealed that a subpopulation of the PuHu26 family contains EcoRI restriction sites spaced at multiples of approximately 172 bp.

Hemolysin toxin produced and secreted by pathogenic Escherichia coli is one of a family of cytolytic, structurally homologous protein toxins known as RTX (repeats in toxin) toxins. RTX toxins are products of a gene cluster, CABD . The A gene product, nontoxic hemolysin (proHlyA) is made toxic by post-translational fatty acylation of two internal lysine residues. HlyC, C gene product, is essential for acylation, and acyl-acyl carrier protein (ACP) is the acyl donor. HlyB and HlyD are involved in secretion of the toxin. HlyC was thought to serve as an internal protein acyltransferase and remained uncharacterized until now. ProHlyA and HlyC were separately subcloned, expressed, and purified, and acyl-ACPs with diverse radioactive acyl groups were synthesized. With these proteins, the conversion of proHlyA to HlyA by acyltransfer was assayed. Acyl-ACP was the obligate acyl donor. Acyltransfer was catalyzed by HlyC monomer, and an acyl-enzyme intermediate was detected and shown to catalyze the reverse reaction. The reaction mechanism was examined by steady state kinetics, and the nature of inhibitions by reaction products was determined. The kinetic mechanism of the internal protein acylation was compatible with an uni uni iso uni uni ping pong with isomerization of the F form of the enzyme. Clues to the chemical mechanism for the acyltransferase were elucidated by both chemical modification studies and site directed mutagenesis of the enzyme. Chemical modification experiments ruled out any critical cysteines, serines, and lysine residues, but suggested a role for histidine(s) and tyrosine(s) in acyltransferase function. In order to examine the function of specific residues and possibly corroborate the chemical findings, site directed mutagenesis studies of the acyltransferase were employed. Seventeen residues that were conserved among 13 different RTX toxin acyltransferases were individually mutated, and the respective HlyCs expressed, and characterized. Residues that were critical for acyltransferase function included Gly 11, His 23, Tyr 70, and Gly 85. As with chemical modification data, mutagenesis ruled out any conserved, essential, cysteines or serines critical for HlyC acyltransferase activity.

By the near-field measurement of the electric field distribution inside the finite width THz parallel plate waveguide, we find the transition from conventional diffractive TEM-like mode to plasmonic mode. This mode transition depends on the geometry of the waveguide. The measurement is conducted on THz-TDS system with scattering probe-technique. We present the simulation which agrees with our experimental data

Composite fibers comprised of 5:95 wt ratio of ultra-short single walled carbon nanotubes (US-SWCNT):polyacrylonitrile (PAN) were spun using a dry-jet wet-spinning method followed by oxidative stabilization at 285 °C. The as-spun and stabilized composite fibers exhibited a 50 and 40 % increase, respectively, in modulus when compared to neat PAN. The vacuum pressure impregnation (VPI) method was employed to reinforce SWCNT fibers. SWCNT fibers were impregnated with polyamic acid (PAA) solution at 100 psi followed by thermal imidization to obtain fibers reinforced with polyimide (PI). The tensile strength was increased form 68 to 215 MPa for SWCNT fibers after VPI and imidization. Surfactant-wrapped chemically converted graphene (CCG) sheets obtained from the hydrazine reduction of GO were functionalized by treatment with aryl diazonium salts. The functionalized nanosheets disperse readily in polar aprotic solvents. A one-pot method has also been developed for reducing GO and simultaneously functionalizing it with alkyl and aryl groups. The alkyl functionalized reduced GO shows higher solubility in organic solvents when compared to GO. Graphene-filled PI composite films were prepared by solution blending of GO and PAA, casting the mixture and imidizing the films by heating up to 400 °C resulting in composite films that exhibit up to a ∼75 % increase in modulus and low moisture uptake. At 2 wt % loading GO, the composite films exhibit a conductivity of 1.25 × 10 -5 S/cm. The layer-by-layer (LbL) assembly technique was also employed in the fabrication of thin film composites of CCG and PI. The assembly was driven by the acid-base interaction between the aniline moieties on functionalized CCG and the carboxyl groups of the PAA. A simple fluid-phase processing method to obtain single to few layers of graphene without the aid of sonication has been developed. Graphene is spontaneously exfoliated from graphite and dissolved at isotropic concentrations as high as ∼1000 ppm in chlorosulfonic acid. The dissolution mechanism in superacids is protonation and electrostatic repulsion. The utility of this simple exfoliation process is further extended to diazonium functionalization of graphene allowing access to edge-functionalized graphenes with a minimal disruption of the graphitic network on the basal plane.