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This study utilizes Aspen Plus chemical process simulation software (V11), applies uniform nucleation theory and growth kinetics equations, and explores the particle formation mechanism of TiCl[sub.4] hydrolysis to prepare nano TiO[sub.2]. In the water/ethanol system, the effects of the reaction time, reaction temperature, water addition, pH value, and ethanol amount on the crystal nucleation rate and TiO[sub.2] particle distribution (PSD) were studied in detail by adding triethanolamine dropwise and using the Aspen Plus chemical process software simulation calculation method. The calculation results indicate that at room temperature, the formation of TiO[sub.2] crystal nuclei mainly occurs in the first 300 s and then enters the growth stage. The reaction was carried out under neutral conditions at room temperature for 4 h in 1 mL TiCl[sub.4], 6 mL C[sub.6]H[sub.15]NO[sub.3], 15 mL H[sub.2]O, and 30 mL C[sub.2]H[sub.5]OH. The maximum number of particles reached 195 mesh per cubic micrometer, and the particle size after crystal nucleus growth was smaller, with a D[sub.50] of 6.15 nm. The distribution curve shows a normal distribution, which is basically consistent with the experimental results. When studying various factors, it was found that controlling the reaction time within 60 min and maintaining the reaction temperature at room temperature can reduce the particle size D[sub.50] to 2.44 nm. Continuing to adjust the amount of water added, it was found that at 1 mL, D[sub.50] decreased again to 0.19 nm. Adjusting the pH value found that maintaining the neutrality did not change the particle size. Continuing to adjust ethanol, it was found that adding an appropriate amount of ethanol promoted nucleation and growth. At 4 mL, the maximum number of particles reached 199 mesh per cubic micrometer, but D[sub.50] slightly increased to 0.24 nm.

One-hundred percent stereo-complexation in poly(l-lactide) (PLLA)/poly(d-lactide) (PDLA) fibers with non-equivalent molecular weights could be achieved via thermal treatment. Stereo-complexed polylactide (sc-PLA) fibers exhibited excellent hydrolysis resistance and thermal resistance. Till now, preparation of sc-PLA fibers with satisfactory qualities required both PLLA and PDLA with equivalently high molecular weights. Moreover, the high-molecular-weight PDLAs are expensive, restricting industrial-scale production and applications of sc-PLA products. In this study, equal-weight mixtures of low-molecular-weight PDLA (L-PDLA) and high-molecular-weight PLLA (H-PLLA) were melt spun into sc-PLA fibers and then completely stereo-complexed via thermal treatment. The hydrolysis resistance of L3/D1 fibers [PLLA (M.sub.v = 3.0 x 10.sup.5)/PDLA (M.sub.v = 1.0 x 10.sup.5)] was similar to that of L3/D3 fibers [PLLA (M.sub.v = 3.0 x 10.sup.5)/PDLA (M.sub.v = 3.2 x 10.sup.5)], but much higher than that of L3 fibers [PLLA (M.sub.v = 3.0 x 10.sup.5)]. Melting temperature and softening temperature of L3/D1 fibers (223 and 126 °C) were also similar to those of L3/D3 fibers (224 and 131 °C), but higher than that of L3 fibers (172 and 72 °C). Utilizing H-PLLA and L-PDLA to prepare sc-PLA fibers with excellent performance is conducive to the wide industrial application of sc-PLA.

The addition reactions of water, alcohols, and primary and secondary amines to the 10-acetonitrilium derivative of nido-carborane were studied. Hydrolysis of 10-MeC≡N-7,8-C[sub.2]B[sub.9]H[sub.11] results in iminol 10-MeC(OH)=HN-7,8-C[sub.2]B[sub.9]H[sub.11], which, on treatment with a base, gives amide [10-MeC(=O)HN-7,8-C[sub.2]B[sub.9]H[sub.11]][sup.−]. The reactions of 10-MeC≡N-7,8-C[sub.2]B[sub.9]H[sub.11] with alcohols lead to imidates 10-ROC(Me)=HN-7,8-C[sub.2]B[sub.9]H[sub.11] (R = Me, Et) as mixtures of E- and Z-isomers. In the solid state, 10-MeOC(Me)=HN-7,8-C[sub.2]B[sub.9]H[sub.11] adopts E-configuration. The reactions of 10-MeC≡N-7,8-C[sub.2]B[sub.9]H[sub.11] with primary amines result in amidines 10-RNHC(Me)=HN-7,8-C[sub.2]B[sub.9]H[sub.11] (R = Me, Et) as mixtures of E- and Z-isomers. In the solid state 10-EtNHC(Me)=HN-7,8-C[sub.2]B[sub.9]H[sub.11] was found to have the Z-configuration, which is stabilized by intramolecular N-H⋯H-B interactions between the NH group originating from the primary amine and the BH group of the carborane cage. These interactions are rather strong (3.7 kcal/mol) and are likely to persist in solution. The reactions of 10-MeC≡N-7,8-C[sub.2]B[sub.9]H[sub.11] with secondary acyclic (Me[sub.2]NH, Et[sub.2]NH) and cyclic (piperidine, morpholine) amines result in amidines 10-R[sub.2]NC(Me)=HN-7,8-C[sub.2]B[sub.9]H[sub.11] (R = Me, Et; R[sub.2] = N(CH[sub.2])[sub.5], N(CH[sub.2]CH[sub.2])[sub.2]O) as single isomers, which, according to single crystal X-ray diffraction data, have the E-configuration.

In gastrointestinal smooth muscle, agonists that bind to G^sub i^-coupled receptors activate preferentially PLC-[beta]3 via G[beta]γ to stimulate phosphoinositide (PI) hydrolysis and generate inositol 1,4,5-trisphosphate (IP^sub 3^) leading to IP^sub 3^-dependent Ca^sup 2+^ release and muscle contraction. In the present study, we identified the mechanism of inhibition of PLC-[beta]3-dependent PI hydrolysis by cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG). Cyclopentyl adenosine (CPA), an adenosine A^sub 1^ receptor agonist, caused an increase in PI hydrolysis in a concentration-dependent fashion; stimulation was blocked by expression of the carboxyl-terminal sequence of GRK2(495-689), a G[beta]γ-scavenging peptide, or G[alpha]^sub i^ minigene but not G[alpha]^sub q^ minigene. Isoproterenol and S-nitrosoglutathione (GSNO) induced phosphorylation of PLC-[beta]3 and inhibited CPA-induced PI hydrolysis, Ca^sup 2+^ release, and muscle contraction. The effect of isoproterenol on all three responses was inhibited by PKA inhibitor, myristoylated PKI, or AKAP inhibitor, Ht-31, whereas the effect of GSNO was selectively inhibited by PKG inhibitor, Rp-cGMPS. GSNO, but not isoproterenol, also phosphorylated G[alpha]^sub i^-GTPase-activating protein, RGS2, and enhanced association of G[alpha]^sub i3^-GTP and RGS2. The effect of GSNO on PI hydrolysis was partly reversed in cells (i) expressing constitutively active GTPase-resistant G[alpha]^sub i^ mutant (Q204L), (ii) phosphorylation-site-deficient RGS2 mutant (S46A/S64A), or (iii) siRNA for RGS2. We conclude that PKA and PKG inhibit G[beta]γ^sub i^-dependent PLC-[beta]3 activity by direct phosphorylation of PLC-[beta]3. PKG, but not PKA, also inhibits PI hydrolysis indirectly by a mechanism involving phosphorylation of RGS2 and its association with G[alpha]^sub i^-GTP. This allows RGS2 to accelerate G[alpha]^sub i^-GTPase activity, enhance G[alpha][beta]γ^sub i^ trimer formation, and inhibit G[beta]γ^sub i^-dependent PLC-[beta]3 activity.[PUBLICATION ABSTRACT]

In the starch processing industry including the food and pharmaceutical industries, α-amylase is an important enzyme that hydrolyses the α-1,4 glycosidic bonds in starch, producing shorter maltooligosaccharides. In plants, starch molecules are organised in granules that are very compact and rigid. The level of starch granule rigidity affects resistance towards enzymatic hydrolysis, resulting in inefficient starch degradation by industrially available α-amylases. In an approach to enhance starch hydrolysis, the domain architecture of a Glycoside Hydrolase (GH) family 13 α-amylase from Aspergillus niger was engineered. In all fungal GH13 α-amylases that carry a carbohydrate binding domain (CBM), these modules are of the CBM20 family and are located at the C-terminus of the α-amylase domain. To explore the role of the domain order, a new GH13 gene encoding an N-terminal CBM20 domain was designed and found to be fully functional. The starch binding capacity and enzymatic activity of N-terminal CBM20 α-amylase was found to be superior to that of native GH13 without CBM20. Based on the kinetic parameters, the engineered N-terminal CBM20 variant displayed surpassing activity rates compared to the C-terminal CBM20 version for the degradation on a wide range of starches, including the more resistant raw potato starch for which it exhibits a two-fold higher Vmax underscoring the potential of domain engineering for these carbohydrate active enzymes.

Heat shock protein 90 (Hsp90) is an ATP-dependent molecular chaperone which is essential in eukaryotes. It is required for the activation and stabilization of a wide variety of client proteins and many of them are involved in important cellular pathways. Since Hsp90 affects numerous physiological processes such as signal transduction, intracellular transport, and protein degradation, it became an interesting target for cancer therapy. Structurally, Hsp90 is a flexible dimeric protein composed of three different domains which adopt structurally distinct conformations. ATP binding triggers directionality in these conformational changes and leads to a more compact state. To achieve its function, Hsp90 works together with a large group of cofactors, termed co-chaperones. Co-chaperones form defined binary or ternary complexes with Hsp90, which facilitate the maturation of client proteins. In addition, posttranslational modifications of Hsp90, such as phosphorylation and acetylation, provide another level of regulation. They influence the conformational cycle, co-chaperone interaction, and inter-domain communications. In this review, we discuss the recent progress made in understanding the Hsp90 machinery.

The role of pyruvic acid (PA), one of the most abundant α-keto carboxylic acids in the atmosphere, was investigated both in the SO.sub.3 hydrolysis reaction to form sulfuric acid (SA) and in SA-based aerosol particle formation using quantum chemical calculations and a cluster dynamics model. We found that the PA-catalyzed SO.sub.3 hydrolysis is a thermodynamically driven transformation process, proceeding with a negative Gibbs free-energy barrier, ca. -1 kcal mol.sup.-1 at 298 K, â¼ 6.50 kcal mol.sup.-1 lower than that in the water-catalyzed SO.sub.3 hydrolysis. Results indicated that the PA-catalyzed reaction can potentially compete with the water-catalyzed SO.sub.3 reaction in SA production, especially in dry and polluted areas, where it is found to be â¼ 2 orders of magnitude more efficient that the water-catalyzed reaction. Given the effective stabilization of the PA-catalyzed SO.sub.3 hydrolysis product as SAâ«PA cluster, we proceeded to examine the PA clustering efficiency in a sulfuric-acid-pyruvic-acid-ammonia (SA-PA-NH.sub.3) system. Our thermodynamic data used in the Atmospheric Cluster Dynamics Code indicated that under relevant tropospheric temperatures and concentrations of SA (10.sup.6 molec.cm-3), PA (10.sup.10 molec.cm-3) and NH.sub.3 (10.sup.11 and 5 x 10.sup.11 molec.cm-3), PA-enhanced particle formation involves clusters containing at most one PA molecule. Namely, under these monomer concentrations and 238 K, the (SA).sub.2 â«PAâ«(NH.sub.3).sub.2 cluster was found to contribute by â¼ 100 % to the net flux to aerosol particle formation. At higher temperatures (258 and 278 K), however, the net flux to the particle formation is dominated by pure SA-NH.sub.3 clusters, while PA would rather evaporate from the clusters at high temperatures and not contribute to the particle formation. The enhancing effect of PA was examined by evaluating the ratio of the ternary SA-PA-NH.sub.3 cluster formation rate to binary SA-NH.sub.3 cluster formation rate. Our results show that while the enhancement factor of PA to the particle formation rate is almost insensitive to investigated temperatures and concentrations, it can be as high as 4.7 x 10.sup.2 at 238 K and [NH.sub.3 ] = 1.3 x 10.sup.11 molec.cm-3. This indicates that PA may actively participate in aerosol formation, only in cold regions of the troposphere and highly NH.sub.3 -polluted environments. The inclusion of this mechanism in aerosol models may reduce uncertainties that prevail in modeling the aerosol impact on climate.