Enantioselective interactions of inversion-labile trigonal iron(II) complexes upon binding to DNA

We studied the interactions of the substitution-inert inversion-labile complexes Fe(bipy) and Fe(phen) [and the inversion-stable complex Ru(bipy)] with DNA. The association of these complexes to DNA is mainly electrostatic, and Fe(phen) shows a more effective binding to DNA than the two bipyridyl complexes, possibly owing to a different binding mode. The interactions are enantioselective, leading to a Pfeiffer shift in the diastereomeric inversion equilibria and an excess of the Δ-enantiomer of Fe(phen) and Fe(bipy), which is directly monitorable through CD. The partition constants for the inversion equilibrium range from 1.3 to 2.0 for Fe(bipy) and Fe(phen), depending on ionic conditions. From flow LD information about the orientation of the complexes on DNA was obtained: it is consistent with a fit of the Δ-enantiomer in the major groove of the right-handed DNA helix. The mechanisms of interaction are discussed against equilibrium, spectroscopic, and kinetic data.     

Conformation of poly(L-arginine). I. Effects of anions

The conformational transition of poly(L -agrignine) by binding with various mono-, di-, and polyvalent anions, especially with SO, was studied by CD measurements. The intramolecular random coil-to-α-helix conformational transition and the subsequent transition to the β-turn-like structure was caused by binding with SO. The binding data obtained from equilibrium dialysis experiments showed that the α-helical conformation of poly(L -arginine) is stabilized at a 1:3 stoichiometric ratio of bound SO to arginine residue; at higher free SO concentrations, the α-helix converts to the β-turn-like structure accompanied by a decrease in amount of bound SO. The same conformaitonal transition of poly(L -arginine) also occurred in the solutions of other divalent anions (SO, CO, and HPO) and polyvalent anions (P₂O, P₃O). Among the monovalent anions examined, CIO and dodecyl sulfate were effective in including α-helical conformation, while the other monovalent anions (OH^?, Cl^?, F^?, H₂PO, HCO and CIO) failed to induce poly(L -arginine) to assume the α-helical conformation. Thus, we noticed that, except for dodecyl sufate, the terahedral structure is common to the α-helix-forming anions. A well-defined model to the α-helical poly(L -arginine)/anion complex was proposed, in which both the binding stoichiometry of anions to the arginine residue and the tetrahedral structure of anions were taken into consideration. Based on these results, it was concluded that the tetrahedral-type anions stabilize the α-helical conformation of poly(L -arginine) by crosslinking between two guanidinium groups of nearby side chains on the same α-helix through the ringed structures stabilized by hydrogen bonds as well as by electrostatic interaction. Throughout the study it was noticed that the structural behavior of poly(L -arginine) toward anions is distinct from that of poly(L -lysine).     

Chemiluminescence of human bloodstream monocytes and neutrophils: An unusual oxidant(s) generated by monocytes during the respiratory burst

Maximal rates of O and H₂O₂ production by human bloodstream monocytes activated during the respiratory burst by phorbol ester were only about 10% of those of neutrophils. Furthermore, monocytes possess only about 5% of the myeloperoxidase activity of neutrophils and so can only produce low levels of HOCI and related compounds. These combined reductions in O generating ability and lower myeloperoxidase levels result in low luminol chemiluminescence stimulated during the respiratory burst of monocytes. However, although monocytes generate much lower levels of O and H₂O₂ than neutrophils, these cells produce comparable rates of PMA-stimulated lucigenin chemiluminescence. Hence, this assay does not accurately reflect the production of either of these two oxidants by activated phagocytes, and further lucigenin must react with some other oxidant(s) via a process which leads to photon emission. This oxidant(s) is not O, H₂O₂, · OH, ¹O₂ or NO, but is derived from O generated during the respiratory burst and is generated in greater quantities by activated monocytes compared with neutrophils. Thus, lucigenin chemiluminescence is an indirect measure of superoxide release.     

A stereospecific complex of poly(I) with ammonium ion

We describe conditions which lead to complete helix formation of poly(I) in the presence of NH. Binding of NH is shown to be specific in the presence of Li⁺, which does not by itself support helix formation under these conditions. The NH–poly(I) complex is characterized by uv, CD, and ir spectroscopy. The CD spectrum is strikingly different from those of the Na⁺ or K⁺ complexes, the first extremum being changed from negative for the metal ions to positive for NH. A stereospecific model is proposed for the NH–poly(I) helix in which the N of NH is located on the axis of the four-stranded helix, midway between planar tetramers formed by the bases. The model is consistent with the tetrahedral symmetry of NH, the requirement for four acceptable hydrogen bonds, the observed stability of the helix, and the accepted geometry of the backbone.     

Number of binding sites of DNA and polynucleotides with tris(2,2'-dipyridyl)ruthenium(II) cations

The binding of tris(2,2′-bipyridyl)ruthenium(II) cations [Ru(bpy)] with single- and double-stranded (ss and ds) DNA, and the polynucleotides poly(A), poly(C), poly(G), poly(I), poly(I) · poly(C), and poly(U), was studied in aqueous solution. Steady-state electrical conductivity measurements with the polynucleotides, ssDNA, and dsDNA reveal that approximately three nucleotides offer one binding site. This may be compared with the ratio [nucleotide]/[Mg²⁺] of 2.4 : 1 for dsDNA. After laser excitation (353 nm), the luminescence of Ru(bpy) bound to nucleic acids shows two decay components. The contribution of the fast component, which is interpreted as resulting from quenching processes of the absorbed ruthenium complex, exhibits a maximum with increasing [nucleotide]/[Ru(bpy)] at a ratio of about three to one. Bound Ru(bpy) can be released from the strand by addition of NaClO₄ [half-concentration: 2.5 and ≤ 10 mM for poly(U) and dsDNA, respectively].     

Comparative biochemical and cytochemical studies on superoxide and peroxide in mouse macrophages

Maximal rates of superoxide (O) release, and the cytochemical locales of peroxide staining in resident, elicited, and activated macrophages have been determined. Macrophages elicited into the peritoneum with either casein (1.2% w/v) or proteose-peptone (10.0% w/v) release about twice as much O as macrophages activated by infection of the animals with either Listeria monocytogenes, or Bacille Calmette-Guerin (BCG) followed by immune boosting with Purified Protein Derivative (PPD) (i.e., about 35 vs. 14–18 nmol O/min/10⁷ cells). Macrophages elicited with thioglycollate (3.0% w/v) and resident macrophages produce negligible amounts of O upon stimulation with PMA. These data are compared with those reported by other investigators who used different procedures. A cytochemical procedure for localizing peroxide has been modified for use with murine macrophages. No production of H₂O₂ by macrophages is detected cytochemically in the absence of stimulation. Upon exposure to PMA, resident macrophages are still largely unresponsive. Approximately 20% of the casein elicited macrophages and BCG-PPD activated macrophages exhibit H₂O₂ staining, which is largely restricted to the cytoplasmic vesicles and channels induced by PMA in these cells. The only exception to this staining pattern is a small population (about 2%) of activated macrophages which exhibits H₂O₂ staining in the cytoplasmic vesicles and channels and on the plasmalemma as well.     

Optimum Designs for Estimating the Variance Components in a Simple Variance Component Model (Model II), I

The methods of optimal designing of experiments proposed by WALD (1943) are used for determination of an A_σ2-optimal concrete design for estimation of σ^2′ = (σ, σ) in case of one-way analysis of variance. Starting point of definition of the optimality criterion is a quadratic loss matrix.     

On the blue color of triiodide ions in starch and starch fractions. I. Characterization and assignment of absorption and circular dichroism spectra of triiodide ions in amylose

Four fundamental Raman lines were observed at 159, 111, 55 and 27 cm^-1 corresponding to the I bound (I) in amyloses with DP from 20 to 100, regardless of the degree of polymerization of I and the excitation wavelength. The spectral resolution was based on the molar extinction coefficient and molar ellipticity spectra of I. Eight bands, named, S₁, S₂, ?, S₈ from long to short wavelength, were isolated. These were found regardless of the DP. By a resonance excitation Raman study, the characteristics of S₃ and S₄, comprising the shoulder around 480 nm, were found to be different from those of S₁ and S₂, comprising the blue band. The assignment of the spectra was based on the electronic states of the monomeric I in the exciton-coupled dimeric unit. It was concluded that the blue band (S₁,S₂) belonged to the long-axis transitions and the shoulder band (S₃,S₄) to the short-axis ones on the monmeric coordinate system.     

Collapse of DNA caused by trivalent cations: pH and ionic specificity effects

A comparison of the condensation of T4 phage DNA by spermidine and Co(NH₃) at pH values between 5.1 and 10.2 has been made using quasielastic light scattering to determine translational diffusion coefficients and Stokes radii. Co(NH₃) is more effective than spermidine in causing condensation at all pH, indicating that the differences observed in previous work were not due to pH effects, as might have been inferred from recent theories of intermolecular forces. The DNA particles collapsed with Co(NH₃) are smaller than those obtained with spermidine. The hydrodynamic radius of spermide-collapsed structures decreases slightly with increasing pH, while the size of the Co(NH₃)collapsed structures is almost independent of pH. These results confirm that there are specific ion effects in DNA condensation by oligocations, in addition to the dominant general polyelectrolyte effects.     

How Large is the Probability for the Estimate of a Variance Component to be Negative?

For a balanced one-way classification, where the normally distributed observations obey a random model y_ij=μ+b_i+c_ij with two variance components var (b_i) = δ and var (c_ij) = δ, the probability is given that the analysis of variance estimate of δ will be negative. This probability depends on δ/δ and the degrees of freedom in the ANOVA table. Tables for this probability are given. If the normally distributed observations obey an intra-class correlation model, the probability that the Mean Square between groups is smaller than the Mean Square within groups can also be evaluated from the given tables.     

High-resolution nmr study of yeast tRNA and the native and denatured conformers of yeast tRNA

The high-resolution nmr spectrum of baker's yeast tRNA, a recently sequenced non-denaturable tRNA, has been compared with the spectra of the native and denatured conformers of the closely related species tRNA. Because of the presence of many common base pairs in the different tRNA's, it is possible to assign most of the low-field resonances to specific secondary-structure base pairs. A comparison of the observed positions of the various resonances with those predicted by a semiempirical ring-current shift theory shows a root-mean-square deviation of 0.14, 0.11, and 0.12 ppm for tRNA (native), and tRNA (denatured), respectively. These results support the ring-current shift theory currently used to interpret the low-field nmr spectra of the tRNA molecules. Differences between the predicted and observed positions of some resonances provide new evidence for higher order effects such as shifts from second nearest neighbors, anomalous shifts exerted by G·U base pairs, and tertiary-structure effects. A model that was previously proposed for the denatured conformer of tRNA is also supported.     

Apparent molar volumes of some amino acids and peptides in aqueous urea solutions

Densities of solutions of several α-amino acids and peptides in 3 and 6m aqueous urea solvents have been determined at 298.15 K. These data have been used to evaluate the infinite-dilution apparent molar volumes of the solutes and the volume changes due to transfer (V ) of the α-amino acids and peptides at infinite dilution from water to aqueous urea solutions. The sign and magnitude of the V values have been rationalized in the framework of Friedman's cosphere-overlap model. The V values for the glycyl group (? CH₂CONH? ) and alkyl side chains have been estimated.     

Physical association of two simple alkylators to some DNA sequences

Molecular mechanics calculations have been used to determine the preferred physical association sites of the known alkylating agent dimethyl aziridinium ion (Az⁺) and a CH prototype test probe with B-form, tetrameric DNA sequences. Electrostatic interactions are most important in determining these preferential physical association sites. In turn, the intermolecular energy minima depend on the charge distribution assigned to the DNA sequence. However, for three reported DNA charge distributions, only two distinct sets of energy minima were obtained for the CH-like ion interacting with (G-C)₄, (A-T)₄, and [(G-C)·(A-T)]₂ deoxyribonucleic acids. These minima correspond to physical association geometries in which the CH-like ion is near known alkylation sites. The results of the Az⁺ … [(G-C)·(A-T)]₂ interaction are virtually identical to those found for the CH-like ion. Aqueous solvation energetics have little effect on the physical association of Az⁺ with [(G-C)·(A-T)]₂.     

Conformational analysis of acetyl-L-phenylalanine p-acetyl and p-valeryl anilides

Empirical force-field calculations and ir and ¹H-nmr spectra indicate that five-membered (C₅) and seven-membered (C) hydrogen-bonded rings are the preferred conformations of acetyl-L -Phe p-acetyl and p-valeryl anilides in nonpolar media. The C₅/C ratio was found to be dependent on the dryness of the solute and the solvent. This fact and the results from conformational-energy calculations suggest that a molecule of water participates in the stabilization of the C conformation.     

A kinetic analysis of hepatic microsomal activation of parathion and chlorpyrifos in control and phenobarbital-treated rats

A kinetic analysis of cytochrome P450-mediated desulfuration (activation) or dearylation (detoxication) showed that rat hepatic microsomes have a greater capacity to detoxify and a lower capacity to activate chlorpyrifos compared to parathion. Kinetic curves for the desulfuration of both parathion and chlorpyrifos were biphasic; K s of 0.23 and 71.3 μM were calculated for parathion, and 1.64 and 50.4 μM for chlorpyrifos. While phenobarbital (PB) exposure seemed to generally lower the K_mapp s for desulfuration except for the low K_m activity on chlorpyrifos, the results were not statistically significant. While the low K_m activity contributed 44 and 60% of the control V_max for parathion and chlorpyrifos, respectively, it contributed 50 and 17% in PB-treated rats. These studies have indicated the presence of a low K_m activity capable of functioning at very low substrate concentrations. A single dearylation K was calculated, 56.0 and 9.8 μM for parathion and chlorpyrifos, respectively. Phenobarbital exposure seemed to raise the Ks of dearylation; however, again, the results were not statistically significant. While numerous biochemical factors contribute to the overall toxicity levels of phosphorothionate insecticides, the in vitro efficiencies of hepatic microsomal desulfuration and dearylation of parathion and chlorpyrifos correspond to the acute toxicity levels.     

Construction of Equi-replicated Balanced Block Designs with Block Sizes Exceeding the Number of Treatments

In this note it is shown that the block design with incidence matrix Ñ = [NN… N], where N = c_1hN_h + c_oh (11′–N_h). c_oh and c_1h are any non-negative integers and N_h,h = 1, 2,…,p, are incidence matrices of balanced incomplete block designs with the same number of treatments t, is a balanced block design with the block sizes exceeding the number of treatments. In derivation the matrix M₀, introduced by CALIński (1971) is utilized.     

Equi-replicated balanced block designs generated by a balanced matrix

In this paper it is shown that if N= \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^{S_h} $\end{document} c_ihN_ih, where c_ih are some non-negative integer numbers and N_ih are such incidence matrices that A_h = \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \sum \limits_{i = 1}^{S_h} $\end{document} i N_ih is a balanced matrix defined by SHAH (1959), for h = 1, 2,…, p, then a block design with an incidence matrix Ñ = [N, N,…,N] is an equi-replicated balanced block design. Here the balance of a block design is defined in terms of the matrix M₀ introduced by CALI?SKI (1971).     

Effects of temperature on microbial ethanol production. II. A thermodynamic interpretation of the temperature profile curve of ethanol production

An attempt is made to give a thermodynamic interpretation of the complete temperature profile curve of ethanol formation. Taking into consideration an enhancing competition between thermal activation and thermal deactivation of ethanol formation at increasing temperatures and supposing that the ethanol production is affected by a reversible and an irreversible term of thermal deactivation of a modified ARRHENIUS equation being current for the total biokinetic sphere may be derived: . The quantities ΔH and ΔH^D_2T are identical with the temperature functions of the change of entropy caused by reversible and irreversible deactivation of ethanol formation, respectively. Accordingly for the yeast strain Saccharomyces cerevisiae Sc 5 the calculated entropy coefficients of reversible and irreversible thermal deactivation of ethanol formation amount to C = (0.245± 0.013) kJ/mol · deg.² and C = (1.657 ± 0.046) kJ/mol · deg.².     

Application of the nearest-neighbor Ising model to the helix-coil transition of polypeptides in mixed organic solvents.

Using the formalism of nearest-neighbor Ising model and assuming that the allowed states for a monomeric unity of a polypeptide chain in solutions containing strong acids are E (helix), C (coil), and CS (solvent-bonded coil), the partition function of the system was deduced analytically. Equations were obtained which permitted the prediction of the characteristic thermodynamic behavior of the helix–coil transition under these conditions. These equations were used to examine critically the possible correlations between experimental data obtained using different techniques. Particular attention was devoted to quantities called “transition enthalpies,” obtained from the slope of the transition curves at the point where the helix fraction is one-half (ΔH), or for measurements of the heat of solution of the polymer over the total range of solvent composition (ΔH), or from heat capacity measurements taken at various temperatures (ΔH). Literature data of ΔH(j = opt, sol, cal) for the system poly-γ-benzyl-L -glutamate in mixtures of dichloroacetic acid and 1,2-dichloroethane were carefully analyzed.