Improvement of activity and stability of chloroperoxidase by chemical modification

<p>Abstract</p> <p>Background</p> <p>Enzymes show relative instability in solvents or at elevated temperature and lower activity in organic solvent than in water. These limit the industrial applications of enzymes.</p> <p>Results</p> <p>In order to improve the activity and stability of chloroperoxidase, chloroperoxidase was modified by citraconic anhydride, maleic anhydride or phthalic anhydride. The catalytic activities, thermostabilities and organic solvent tolerances of native and modified enzymes were compared. In aqueous buffer, modified chloroperoxidases showed similar <it>K</it>_mvalues and greater catalytic efficiencies <it>k</it>_cat/<it>K</it>_mfor both sulfoxidation and oxidation of phenol compared to native chloroperoxidase. Of these modified chloroperoxidases, citraconic anhydride-modified chloroperoxidase showed the greatest catalytic efficiency in aqueous buffer. These modifications of chloroperoxidase increased their catalytic efficiencies for sulfoxidation by 12%~26% and catalytic efficiencies for phenol oxidation by 7%~53% in aqueous buffer. However, in organic solvent (DMF), modified chloroperoxidases had lower <it>K</it>_mvalues and higher catalytic efficiencies <it>k</it>_cat/<it>K</it>_mthan native chloroperoxidase. These modifications also improved their thermostabilities by 1~2-fold and solvent tolerances of DMF. CD studies show that these modifications did not change the secondary structure of chloroperoxidase. Fluorescence spectra proved that these modifications changed the environment of tryptophan.</p> <p>Conclusion</p> <p>Chemical modification of epsilon-amino groups of lysine residues of chloroperoxidase using citraconic anhydride, maleic anhydride or phthalic anhydride is a simple and powerful method to enhance catalytic properties of enzyme. The improvements of the activity and stability of chloroperoxidase are related to side chain reorientations of aromatics upon both modifications.</p

Green's functions of multiband non-Hermitian systems

Green's functions of non-Hermitian systems play a fundamental role in various dynamical processes. Because non-Hermitian systems are sensitive to boundary conditions due to the non-Hermitian skin effect, open-boundary Green's functions are closely related to the non-Bloch band theory. While the exact formula of open-boundary Green's functions in single-band non-Hermitian systems proves to be an integral along the generalized Brillouin zone (GBZ), the proper generalization in generic multiband systems remains unclear. In this work, we derive a formula of open-boundary Green's functions in multiband non-Hermitian systems by viewing the multiband GBZ on the Riemann surface. This formula can be applied to describe directional amplification in multiband systems, which can be verified at various experimental platforms.Comment: 7 pages, 4 figure

Danshensu exerts cardioprotective effects in rats with acute myocardial infarction via reduction of infiltration of inflammatory cells and mitigation of myocardial fibrosis

Purpose: To investigate the mitigative impact of danshensu on heart tissues in acute myocardial infarction (AMI) rats, and the mechanism of action involved. Methods: Seventy-five male Sprague-Dawley (SD) rats were used in this study. After successful induction of myocardial infarction, the rats were divided into model group (MG), low-dose danshensu group (LDG; 15 mg/kg), middle-dose danshensu group (MDG; 30 mg/kg), and high-dose danshensu group (HDG; 60 mg/kg), with 15 rats per group. Rats in sham group (SG; n = 15) served as control. Serum levels of biochemical indicators and expressions of various proteins in myocardial tissue were determined using Western blotting, and compared amongst the rat groups. Results: Serum cTnI concentrations in MDG and HDG were significantly decreased, relative to the corresponding concentrations in MDG. There were significantly lower serum concentrations of IL-1 in MDG and HDG than in model rats. Rats in HDG had lower serum IL-6 concentration than MG rats, while TNF-α levels were down-regulated in MDG and HDG, relative to MG (p &lt; 0.05). Conclusion: Danshensu protects the heart function of rats with AMI by decreasing inflammationderived cells and mitigating myocardial fibrosis. Thus, it may be useful in the management of AMI in humans but clinical trials are necessary to ascertain this. Keywords: Danshens; Acute myocardial infarction; Myocardial ischemia-reperfusion; Myocardial fibrosi

Quaternary amines exert anti-myocardial ischemia effects via regulation of energy metabolism and oxygen free radicals in myocardial cells in acute myocardial infarction rats

Purpose: To investigate the effect of quaternary amines on myocardial cells of a rat model of cardiac arrest, with respect to energy generation potential and oxygen free radicals. Methods: Forty-five Sprague-Dawley (SD) rats were assigned to sham, model and quaternary amine groups (each with 15 rats). After their corresponding treatments, lectrocardiogram (ECG) monitoring of the rats in the three groups at various time periods was carried out. Serum levels of myocardial enzymes, thromboxane B2 (TXB2), prostacyclin I2 (PGI2), serum carbon monoxide (CO), and changes in endothelial carbon monoxide synthase (eNOS) and endothelin (ET), were determined. Results: The levels of NO and eNOS were significantly reduced in model rats, relative to sham operation rats, while ET was significantly elevated in sham rats (p &lt; 0.05). There were higher levels of NO and eNOS in the quaternary amine group than in model rats, but ET was higher in quaternary amine group than in model rats. Thromboxane B2 (TXB2) concentration was higher in model rats than in sham rats (p &lt; 0.05). While PGI2 was markedly lower in quaternary group than in sham operation rats. TXB2 was lower in the quaternary amine group than in model rats, while PGI2 was significantly higher in quaternary amine group, relative to model rats (p &lt; 0.05). Conclusion: Quaternary amines exert anti-myocardial effects by regulating energy metabolism and oxygen free radicals in myocardial cells of congestive heart failure rats, and thus are potentially useful for the management of acute myocardial infarction. Keywords: Quaternary amine; Acute myocardial infarction; Electrocardiogram; Serum myocardial enzymes; Myocardial cell

Troponin T3 regulates nuclear localization of the calcium channel Cavβ1a subunit in skeletal muscle

The voltage-gated calcium channel (Cav) β1a subunit (Cavβ1a) plays an important role in excitation-contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Cavβ1a subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160-244 aa) and Cavβ1a NH2-terminus (1-99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Cavβ1a/YFP shows that TnT3 facilitates Cavβ1a nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation.Fil: Zhang, Tan. Wake Forest School of Medicine; Estados UnidosFil: Taylor, Jackson. Wake Forest School of Medicine; Estados UnidosFil: Jiang, Yang. Wake Forest School of Medicine; Estados UnidosFil: Pereyra, Andrea Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Messi, Maria Laura. Wake Forest School of Medicine; Estados UnidosFil: Wang, Zhong Min. Wake Forest School of Medicine; Estados UnidosFil: Hereñú, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner". Universidad Nacional de la Plata. Facultad de Ciencias Médicas. Instituto de Investigaciones Bioquímicas de La Plata ; ArgentinaFil: Delbono, Osvaldo. Wake Forest School of Medicine; Estados Unido