Some features of hydrolysis of the hybrid B-Z-form dna by serratia marcescens nuclease

Highly polymerized herring testis DNA of the random nucleotide sequence was used as a model of natural substrate to study some features of hydrolysis of the hybrid B-Z form with Serratia marcescens nuclease. The hybrid B-Z-form was formed upon addition of 1.15. M MgSO4 and 0.421 mM Co(NH3)6Cl3. The DNA transition from the right handed B-form to the hybrid B-Z-form caused a decrease in Vmax of DNA cleavage with the nuclease. The diminishing Vmax was consistent with diminishing values of Km and Kcat. The binding of Mg2+ or Co(NH3)6 3+ to highly polymerized DNA caused correspondingly about 80-or 7-fold decrease in Km and more than 1600 or 600 decrease in Kcat compared with that of Mg-DNA complex of B-form. © 2014 Science Publication

Action of hexaamminecobalt on the activity of Serratia marcescens nuclease

Using CD spectroscopic and kinetic analysis, a refined mechanism of Co(NH3)6 3+ action on activity of Serratia marcescens nuclease was elucidated. The mechanism was identical with previously found mechanisms of Mg2+ and C7H5O2Hg+. Similarly to Mg2+ and C7H5O2Hg+, Co(NH3)6 3+ binding to the DNA substrate induced changes in the secondary structure which resulted in changes of the enzymatic activity of the S. marcescens nuclease. Upon binding of 0.03 Co(NH3)6 3+ per DNA phosphate, highly polymerized DNA displayed A-form characteristics. The DNA transition from B-form to A-form intermediate was followed by a decrease of the nuclease activity. The diminishing nuclease activity was consistent with diminishing values of Km and Kcat. Co(NH3)6 3+ binding to the highly polymerized DNA caused a 1.7-2.8-fold decrease in Km, and 13.3-19.9 decrease in Vmax compared with Mg-DNA complex. A vast excess of Co(NH3)63+ did not affect the activity of S. marcescens nuclease if the DNA in the assay mixture remained in its B-form conformation. Preincubation of S. marcescens nuclease with Co(NH3)6 3+ did not influence the tertiary structure of the enzyme

Metal binding induces conversion of B- to the hybrid B-Z-form in natural DNA

Highly polymerized herring testis DNA of the random nucleotide sequence has been studied in solution by circular dichroism and ultra-violet absorption spectrometry under various experimental conditions. At low temperature upon addition of 0.05 M NaCl or 1.15 M MgSO4 the DNA formed a helix that belonged to the B-family. As the temperature was increased a transition from the pure B- to the hybrid B-Z-form occurred in the presence of 1.15 M MgSO4. This transition occurred over a large range of temperatures and corresponded to a non-cooperative conformational change. A similar DNA transition was induced with 0.098 mM Co(NH3)6Cl3. However, in the presence of 5.3 M NaCl the DNA conformation was not similar to that observed in 1.15 M MgSO4 or 0.098 mM Co(NH3)6Cl3 independently on the environmental temperature. In 5.3 M NaCl the DNA is thought to undergo a transition from one to another right-handed conformation that could be intermediate partially dehydrated conformer arising on the first step in the sequential transition to the dehydration of the polynucleotide. Our results show that a realistic model of native DNA, bearing Z-tracts embedded in B-helixes, can be obtained upon binding of alkaline earth or transition metals. © 2008 Elsevier B.V. All rights reserved

Metal binding induces conversion of B- to the hybrid B-Z-form in natural DNA

Highly polymerized herring testis DNA of the random nucleotide sequence has been studied in solution by circular dichroism and ultra-violet absorption spectrometry under various experimental conditions. At low temperature upon addition of 0.05 M NaCl or 1.15 M MgSO4 the DNA formed a helix that belonged to the B-family. As the temperature was increased a transition from the pure B- to the hybrid B-Z-form occurred in the presence of 1.15 M MgSO4. This transition occurred over a large range of temperatures and corresponded to a non-cooperative conformational change. A similar DNA transition was induced with 0.098 mM Co(NH3)6Cl3. However, in the presence of 5.3 M NaCl the DNA conformation was not similar to that observed in 1.15 M MgSO4 or 0.098 mM Co(NH3)6Cl3 independently on the environmental temperature. In 5.3 M NaCl the DNA is thought to undergo a transition from one to another right-handed conformation that could be intermediate partially dehydrated conformer arising on the first step in the sequential transition to the dehydration of the polynucleotide. Our results show that a realistic model of native DNA, bearing Z-tracts embedded in B-helixes, can be obtained upon binding of alkaline earth or transition metals. © 2008 Elsevier B.V. All rights reserved

Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens

The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+ and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed

Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens

The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed

EFFECTS OF AMLODIPIN AND METOPROLOL ON AUTONOMIC SYSTEM IN EMOTIONAL AND COLD TESTS IN HYPERTENSIVE PATIENTS WITH DIFFERENT PSYCHOLOGICAL PROFILE

Aim. To asses effects of amlodipin and metoprolol on autonomic system in emotional and cold tests in hypertensive patients with different psychological profile (PP) Material and methods. 61 patients with arterial hypertension of II grade were observed. Therapy with amlodipin or metoprolol was prescribed and allowed to reach target blood pressure (BP) level in all the patients. Patients were divided into 2 groups: 1-st one – patients with normal PP, 2-nd group – patients with subclinical depression. Patients were examined before and 30 days after therapy. Examination included ambulatory BP monitoring, assessment of autonomic status by variational intervalometry and spectral analysis of heart rate variability (HRV) in cold and emotional tests. Depression and anxiety levels were determined with Bek’s and HADS scales.  Results. Treatment with amlodipin  and metoprolol can result in improvement, worsening or unchanging of PP.  In hypertensive patients with subclinical depression improving their PP resulted in autonomic reaction change: sympathetic activity increases and reaction on stress becomes more adequate. If subclinical depression occurred in hypertensive patients because of amlodipin and metoprolol therapy, sympathetic system stress-reaction decreased and parasympathetic influence increased. Conclusion. The study results show necessity of psychometric examination of hypertensive patients in order to reveal subclinical depression and anxiety

Isoforms of Serratia marcescens nuclease. The role of Mg2+ in the hydrolysis mechanism

Structural and functional differences between isoforms Sm1 and Sm2, a lack of influence of free Mg2+ on the isoform structures, formation of DNA-magnesium complex serving with great probability as a real substrate for the nuclcasc has been summarized on the basis of experimental data. Mg2+ forming a complex with phosphate groups of DNA are supposed to further increase the electrophilicity of the phosphorus atoms besides causing a conformational change of the substrate

Outer-sphere interactions between octahedral chiral cobalt(III) complexes and water-soluble calixarenes

The structures and stability of outer-sphere associates of sulfonate derivatives of thiacalix[4]arene and calix[4]resorcinarene with coordinatively saturated cobalt(iii) bis- and tris-chelates ([Co(L-His)2] +, [Co(en)2ox]+, [Co(en)3] 3+, and [Co(dipy)3]3+) were compared based on the data from UV, CD, 1D 1H NMR, and 2D (2D NOESY) 1H NMR spectroscopy and conductometry. Outer-sphere association is accompanied by partial penetration of the chelate rings of the complexes into the hydrophobic cavity of calixarene, which induces changes in the spectroscopic and spectropolarimetric properties of the cobalt(iii) complexes

Cytoprotective effect of fullerene C<inf>60</inf> derivatives with different structures

Transmembrane potential of mitochondria is a sensitive biomarker of metabolic activity of cells. Here, we studied mitochondrial potential Ψm in Yarrowia lipolytica yeast cells treated with two fullerene C60 derivatives: bis-nitroxide methanofullerene and 3-phospho-pentafullerene acid. Transmembrane mitochondrial potential was measured by vital ratiometric cationic fluorochrome JC-1 using flow cytometry. The fullerene C60 derivatives tested in a concentration of 10 μg/ml developed cytoprotective effect in the yeast cells challenged either with non-ionic detergent tween-80, or Tris-buffer, pH 9.0. Treatment with bis-nitroxide methanofullerene resulted in a 6-fold increase in proportion of cells with high Ψm, while 3-phospho-pentafullerene acid evoked a 1,5-fold increase in this subset compared to the stressed cells. Hence, both fullerene derivatives counteract Ψm dissipation in challenged cells