ALBERT

Notes: A major component of pigment gallstones (PS) is a black, insoluble substance. It has been suggested that this pigment material might be a highly crosslinked polymer, and if such were the case, it should imbibe solvent (swell) to the maximum permitted by the crosslinks of its macromolecular network. We measured the equilibrium amount, qeq, by which pulverized, desiccated PS swells in different liquids, including isotonic aqueous buffers at pH values from 1.5-11.5. For ionic strengths ≥ 0.15, the dependence of qeq on pH exhibits a broad titration curve with a midpoint near pH 7. qeq was 〈 1.2 in methanol, dimethylformamide, dimethylsulfoxide, and chloroform. The ir absorbance from vinyl groups in the black pigment was only one-eighth that of unconjugated bilirubin, the primary chemical building block of PS; this implicates vinyl groups in the formation of a polymer network. The rise in qeq with increasing pH suggests that the carboxyl groups are free to ionize and are therefore not involved in the covalent bonds that make the crosslinked polymer. A network polymer structure would account for the inability to dissolve PS in those solvents in which unconjugated bilirubin is soluble.

Notes: 25Mg-nmr data are reported that address the nature of the magnesium ion-DNA interaction. It is found that competitor ions such as calcium, mercury, zinc, and cobalt ions are not effective in competing for all of the magnesium ion-DNA interaction that is reported by the 25Mg-nmr spectrum. The temperature dependence of the 25Mg-nmr spectrum in DNA solution studied at high concentrations of competitor ion indicates that the chemical-exchange lifetime of the magnesium ions at DNA binding sites makes a major contribution to the 25Mg-nmr line width. However, the activation parameters are not consistent with the temperature dependence of either transport properties or chemical exchange with phosphate groups alone, but are consistent with a sum of at least two processes that provide opposing contributions to the 25Mg-nmr relaxation. It is also shown that the non-Lorentzian character of the 25Mg-nmr line previously reported is consistent with the effect of an incompletely averaged static nuclear electric quadrupole interaction and/or an exchange process that is slow with respect to the magnitude of this interaction. Because the concentrations employed in these experiments are high, the present data do not provide a direct or critical test of the electrostatic theories of ion-polyelectrolyte interaction. The present data do demonstrate, however, that such theories alone are insufficient as a basis for understanding the 25Mg-nmr data.

Notes: The persistence length of lugworm cuticle collagen in 0.1M acetic acid was evaluated as 1600 ∼ 1800 Å by Yamakawa-Fujii's model for a wormlike chain from the sedimentation constant and the intrinsic viscosity. The persistence length was further examined for a series of sample “collagen sonicates” produced by varying the duration of sonic irradiation. To estimate the salt effect on the persistence length, measurements were made over a range of NaCl concentrations from 0 to 0.1M. The results showed that the cuticle collagen and collagen sonicates had identical values of persistence length and that the neutral salt effect for the cuticle collagen was far smaller than that for DNA.

Notes: We have used translational diffusion coefficient measurements and subunit hydrodynamic theory to determine the dimensions and shape of bacterioophage T4D baseplates and tails. The diffusion coefficient of the baseplate, measured by quasielastic laser light scattering (QLS), was determined previously by Wagenknecht and Bloomfield to be D = 8.56 × 10-8 cm2/s. For the tail, we found D = 5.88 × 10-8 cm2/s by QLS, and D = 6.02 × 10-8 cm2/s by combining sedimentation coefficient and molecular weight in the Svedberg equation. These values, which have an uncertainty of ±2.7%, when combined with subunit hydrodynamic theory, enabled us to refine estimates of dimensions obtained by electron microscopy. For the hexagonal baseplate, the vertex-to-vertex distance is about 480 Å, the thickness is 160 Å, and there are six extended short fibers 320-Å long and 40 Å in diameter. When a baseplate of these dimensions is attached to a tail tube-sheath-connector complex 1050-Å long and 240 Å in diameter, the calculated D is 5.93 × 10-8 cm2/s, within 1% of experiment. This combined use of electron microscopy and hydrodynamics, using the former to ascertain shape, and the latter to obtain solution dimensions, is a powerful approach to the structure of biomolecular complexes.

Notes: Poly(L-lysine) of various molecular weights between 2700 and 475,000 was spin-labeled. From the electron spin resonance spectra, the degree of freedom of the nitroxide was determined by calculation of the rotational correlation time as the poly(L-lysine) underwent the pH-induced random coil to α-helix conformational transition. In general, the rotational correlation time of the nitroxide increased as the pH was increased, indicating a more restricted environment for the spin label when poly(L-lysine) is deprotonated. For the high-molecular-weight poly(L-lysine) this corresponds to the formation of the α-helix and indicates that the side chain-side chain interaction and decreased segmental motion of the backbone (slightly) restricts the motion of the spin label. For the 2700-molecular-weight poly(L-lysine), previously shown not to assume a helical conformation at high pH, the increase in the rotational correlation time of the spin label indicates that the side chain-side chain interaction takes place after deprotonation but without helix formation. This may indicate that helix formation per se is not needed to produce the observed effect even with the high-molecular-weight polymers. The rotational correlation time of the spin label at a particular pH did not depend on the molecular weight of the poly(L-lysine) over the 200-fold range of molecular weights. This indicates that the rotational correlation time reflects the rotational mobility of the spin label in a localized environment and not the rotational diffusion of the entire macromolecule.

Notes: The interaction of fluoroquinacrine, 3-fluoro-7-chloro-9-(diethylamino-1-methylbutyl-amino)acridine, with poly(A), DNA, and tRNA has been investigated by monitoring changes in the 19F-nmr properties, the fluorescence, and the optical absorbance of the drug. The changes in the properties of fluoroquinacrine in the presence of nucleic acids are similar to those observed for quinacrine and suggest that the drugs bind in a similar fashion. The molecular dynamics of fluoroquinacrine bound to nucleic acids were determined by interpreting the data from a number of different nmr relaxation experiments with a two-correlation-time model. The two motions are the long-range bending motion of the drug-nucleic acid complex and the sliding of the drug between the base pairs. Both dipolar and chemical shift anisotropy contributions to the nmr relaxation parameters were taken into consideration. The binding of fluoroquinacrine to tRNA appears to be different from that observed for binding to DNA. Optical absorbance and 19F-nmr were also used to examine the helix-to-coil transitions of the drug-nucleic acid complexes. In the DNA complex, the 19F chemical shift changes parallel the absorption changes that occur during the transition. 19F-nmr and absorption show that the drug-tRNA complexes undergo a cooperative helix-to-coil transition, with the drug binding sites melting when the tRNA is 70% denatured.

Notes: The crystal structure of the title compound, a model for the glycosyl linkage between the asparagine side chain and N-acetyl glucosamine in glycoproteins, has been determined and compared to other model structures. The pyranose ring in the crystal is in the 4C1 chair conformation and the amide functions at C1 and at C2 are both oriented such that the amide protons are nearly trans to their respective sugar-ring protons. Coupling constants determined from the fully assigned proton nmr spectrum in aqueous solution are consistent with the conformation in the crystal.

Notes: Flow linear dichroic studies have been conducted on phage T4B in its fast and slow forms. The behavior of the phages is well represented by an equivalent ellipsoid model using the Peterlin-Stuart theory. The measurements permit the evaluation of the optical factor of the DNA in the phage and the rotary diffusion coefficient of the phage particle. Both these quantities change during the slow-fast conversion. The rotary diffusion results are in good agreement with those obtained by other workers with other methods. The optical factor is negative, indicating a net alignment of DNA helices parallel to the phage axis. The results exclude certain simplified models for the packaged DNA but do not lead to a unique structural conclusion. The flow dichroism experiment and its interpretation are described, and a simple method of calculating optical factors for complicated but cylindrically symmetric structures is presented.

Notes: It has recently been proposed that the repeating backbone nucleotide may be regarded as consisting of two blocks of equal magnitude representable by two virtual bonds. Implicit consideration of the nucleotide (ψ,ψ) and internucleotide (ω′,ω) geometry that generate variety in polynucleotide conformations, and of the constancy of the repeating structural moieties (P-C4′ and C4′-P) independent of the above rotations, has enabled us to utilize this scheme in the study of ordered structures such as di-, oligonucleotides and, most significantly, tRNA. The polynucleotide folding dictated by short-, intermediate-, and long-range interactions in the monoclinic and orthorhombic forms is described and compared through circular plots depicting the virtual bond torsions and distance plots constructed independently for backbone as well as bases. The torsions and the bond angles associated with the virtual bonds afford a clear distinction between ordered helical segments from loops and bends of tRNA. Lower virtual bond torsions (-60° to 60°) concomitant with higher values of virtual bond angles characterize various bend regions, while torsions around 160°-210° typify ordered helical strands. The distance plot elucidates the type of interaction associated with various sub-structures (helix-helix, helix-loop, and loop-loop) that form the constituents of different structural domains. Several other features such as the manifestation of the P10 loop and the approximate twofold symmetry in the tRNA molecule are conspicuous on the distance plot.

Notes: The probability of DNA base-pair opening was calculated at temperatures below the denaturation region. The helix-coil transition theory, modified to include different nearest-neighbor interactions, was employed. Predictions of base-pair opening employing DNA melting-curve parameters differed considerably from predictions based on parameters evaluated from synthetic RNA oligomer data of Gralla and Crothers (G-C) and formaldehyde-DNA binding experiments of McGhee and von Hippel (M-vH). Calculations based on the latter parameters indicate a base-pair-opening probability of 10-2-10-3 at 35°C in 0.1M NaCl. DNA melting-curve parameters predict values about 103 smaller. At a temperature 10°C below the transition midpoint of a specific DNA sequence, DNA melting parameters predict base-pair opening of about 10-3, whereas the G-C and M-vH parameters predict that ≳0.16 of the DNA is melted. Experiments and theoretical assumptions relevant to the calculations are analyzed. Evidence suggests that DNA melting parameters are valid when the average loop size exceeds some minimum value, whereas the G-C and M-vH parameters appear more valid for single base-pair loops. A reconciliation of the two sets of predictions can be made if interactions extending beyond neighboring base pairs are considered. Such interactions will make the parameters of the nearest-neighbor model appear to change with the average loop size. Experiments that may provide further measurements of base-pair opening are discussed.

Notes: Starting with β-methoxy methacryloylisocyanate, β-methoxy methacrylisothiocyanate, and β-isocyanatopropionyl chloride, on the one hand, and Nα-Z-lysine or Nα-Z-ornithine, on the other hand, Nα-Z-amino acids with pyrimidine bases in the side chain were synthesized. These Z-protected nucleoamino acids were converted to the corresponding N-carboxyanhydrides (NCAs) via the silylester method. In the case of 2-thiothymine derivatives, the reaction intermediate of the NCA synthesis caused benzylation of the thioxo- group, so that a new class of 2-mercaptopyrimidine derivatives was isolated unexpectedly. The poly(nucleoamino acids) obtained by polymerization of the nucleoamino acid NCAs were characterized by elemental analyses, optical rotations 1H-nmr and 13C-nmr spectra. Vapor pressure osmometry revealed that the DPs were in the range of 20-30. Their spectra suggest a helical secondary structure. While all homopolypeptides are insoluble in water, copolypeptides containing L-lysine Nε-hydrobromide possess good solubility in water.

Notes: Vibrational circular dichroism (VCD) spectra for the principal amide stretching vibrations, amide A (N—H stretch) and amide I (predominantly C=O stretch), are presented and analyzed for a variety of polypeptides dissolved in chloroform, as well as for two examples in D2O. Our results for poly(γ-benzyl-L-glutamate) confirm the first and only previous report of VCD in polypeptides carried out by Singh and Keiderling [(1981) Biopolymers 20, 237-240]. Collectively, our spectra show that the sense of the bisignate VCD in these two regions depends on the sense of α-helicity and not on the absolute configuration of the constituent amino acids. This conclusion is established by obtaining VCD for the two polypeptides, poly(β-benzyl-L-asparate) and poly(im-benzyl-L-histidine), that form left-handed as opposed to right-handed α-helices. A new amide band having significant VCD intensity owing to its Fermi resonance interaction with the N—H stretching mode has been identified as a weak shoulder on the low-frequency side of the amide A band near 3200 cm-1 and is assigned as a combination band of the amide I and amide II vibrations. VCD spectra of polypeptides in D2O solution, although weak, have been successfully measured in the amide I region, where spectra appear to be more complicated due to the presence of solvated and internally hydrogen-bonded amide groups. Strong monosignate contributions to the VCD in the amide A and amide I regions for some of the polypeptides indicate coupling of an electronic nature between these two regions and is deduced by an application of the concept of local sum rules of rotational strength. It appears that a detailed understanding of the VCD obtained for polypeptides will not only be diagnostic of secondary structure, but also of more subtle structural and vibrational effects that give rise to local, intrinsic chirality in the amide vibrations.

Notes: A theoretical analysis of the binding curves for the bifunctional peptide antibiotic echinomycin and its analogs interacting with a variety of DNAs is presented. The method is an extension of our previous work using the sequence-generating-function technique and has been modified to allow for consideration of cooperativity within the framework of the neighbor-exclusion rule. Binding by both single and double intercalation is included, and the results are, in many cases, superior to the analysis based on single-mode binding. In all cases the data are consistent with the neighbor-exclusion principle for intercalation when analyzed with this approach, while data analysis, using a simpler method, often led to violation of this rule. Positive cooperativity is considered in the treatment of data for binding to poly(dA-dT). Finally, we discuss the relationship between base specificity and binding site size.

Notes: Quasielastic light scattering and electrophoretic light scattering studies were carried out on mononucleosome and oligonucleosome systems. The electrophoretic light scattering experiments employed static and sinusoidal electric fields. Data are presented that suggest at least two relaxation modes. It is proposed that the small amplitude sinusoidal field effectively polarizes the ion atmosphere about the polyion, thus leading to an induced dipole moment that varies sinusoidally in time. This model is, in essence, an extension of the current interpretation of low-frequency dielectric dispersion data on DNA as being due to fluctuations of counterions along the polyion.

Notes: Human fibrinogen was treated with thrombin in the presence of fibrinoligase (Factor XIIIa) and calcium ion at pH 8.5, ionic strength 0.45, and the ensuing polymerization was interrupted at various time intervals (t) both before and after the clotting time (tc) by solubilization with a solution of sodium dodecylsulfate and urea. Aliquots of the solubilized protein were subjected to gel electrophoresis on polyacrylamide gels after disulfide reduction by dithiothreitol and on agarose gels without reduction. The degree of γ-γ ligation was determined from the former and the size distribution of ligated oligomers, for degree of polymerization x from 1 to 10, from the latter. In some experiments, thrombin was inhibited, after partial polymerization, by p-nitrophenyl-p′-guanidinobenzoate. From these, it was concluded that for thrombin concentration ≤0.013 units/mL and fibrinoligase ≥30 mg/L, oligomer assembly is rapid compared with peptide A release and ligation is rapid compared with assembly. Under these conditions, the theory of the first paper of this series describes rather well the time dependences of the degree of γ-γ ligation, the weight fractions of monomer and small oligomers, and the number- and weight-average degrees of polymerization after solubilization of the staggered overlapped assemblies, each of which splits to give two strands of end-to-end ligated oligomers. The theory assumes that the second A peptide is released by thrombin more rapidly than the first by a factor q, which, from the experimental data, is determined to be 16. The subsequent assembly into staggered overlapped oligomers follows the statistics of linear polycondesation taking into account the presence of both difunctional and monofunctional combining units. For higher thrombin or lower fibrinoligase concentrations, ligation fails to keep pace with oligomer assembly, and the size distributions after solubilization show a higher proportion of very small and a lower proportion of larger ligated oligomers, owing to separation of the staggered overlapped assemblies into smaller fragments.

Notes: A theoretical model to determine the probability of loop formation, based on an elaborated form of the Jacobson-Stockmayer theory of cyclization equilibria, has been developed and used on RNA chains of homogeneous puckering and lengths up to 27 residues. The probability Qx (q, γ0, ε0) of occurrence of hairpin loops of a particular chain x is given by Qx (q, γ0, ε0) = [W (q) δr][2Γq (γ0)δγ] [Eq,γ0 (ε0) δε] where W(q) is the three-dimensional density distribution function of end-to-end vectors r centered about the ideal loop closure position q; Γq(γ0) is an angular correlation factor that restricts the orientation of terminal bonds (i.e., bond x and bond 1) in the loop to a specified value Δθ = cos-1 (γ0) when r adopts a value within a range δr from position q; and Eq,γ0(ε0) is the probability that ε falls within δε of ε0 when r and γ assume the values denoted by the respective subscripts. The parameter ε is related to the angle between a hypothetical bond (x + 1) and bond 1. In these calculations, Eqγ0(ε0) was set equal to 1. For randomly coiling models previously developed to reproduce polynucleotide unperturbed dimensions, loop closure probability is maximized with chains of length 22 residues. Larger hairpin loops of 24-25 residues, also favored in C3′-endo random coils of this type, are potential models of tRNA unfolding. W(q) is a stronger determinant of loop closure than Γq(γ0). The angular correlation effect is most noticeable at chain lengths 22 and 23 where 2Γq(γ0) deviates from unity.

Notes: High-resolution neutron time-of-flight (TOF) spectra were measured for partly deuterated hen egg-white lysozyme in solution with and without N-acetyl-glucosamine inhibitor bound to the cleft, and in polycrystalline form. Weak but reproducible bands occur at frequencies between 25 and 375 cm-1. The bands were tentatively assigned on the basis of previous results for homopolypeptides. At very small energy transfers (between about 1 cm-1 and 40 cm-1), the TOF spectra show a dependence both on inhibitor binding and crystalline environment. This is interpreted in terms of conformational flexibility.

Notes: Transient electric dichroism has been measured for the ferriheme-poly(L-lysine)[(Lys)n], ferroheme-(Lys)n, and ferroheme-(Lys)n-carbon monoxide (CO) solutions at pH 9-12. The Soret absorption maximum in electronic spectrum (λ), the reduced linear dichroism (ρ∞) at complete orientation and the calculated angle (φ) between the porphyrin plane of a bound heme and the oriented polymer axis are determined for the following complexes: a ferriheme-(Lys)n complex at pH 9.5-10.5 (λ = 420 nm, ρ∞ = 0.50, and φ = 19°), a ferroheme-(Lys)n complex at pH 9.5-10.2 (λ = 432 nm, ρ∞ = 0.77, and φ = 0°), and a ferroheme-(Lys)n-CO complex at pH 9.25 (λ = 430 nm, ρ∞ = 0.38, and φ = 24°). Based on the above data, the validity of the structures of heme-(Lys)n complexes proposed by other investigators is discussed.

Notes: The stability of the α-helices of isomeric block copolypeptides is nonequivalent, as reported previously. In order to explore the origin of the nonequivalence, the stability of α-helix of two block copolypeptides, (L-Ala)20-(L-Glu)20-(L-Phe) (designated as AEF) and (L-Glu)20-(L-Ala)20-(L-Phe) (EAF), in aqueous solution was investigated as a function of pH, temperature, and salt concentration by the measurement of the α-helical content using CD at 223 nm. The transition temperature, Tm, as a measure of the stability of the α-helix, decreased with increasing the salt concentration for EAF, while Tm increased for AEF. The results indicate that electrostatic interactions affect the nonequivalence of such helical stability. Thermodynamic quantities, ΔG, ΔH, and ΔS, of the thermal transition from random coil to α-helix were obtained by applying the curve-fitting method to the data. The major contribution to the effects of salts seems to be the entropic term, not the enthalpy term. This is unexpected, since the salt ions would weaken electrostatic interactions between ionized groups and the dipole along the helical axis, which affect the enthalpy term. In addition, the dependence of the electrostatic effect on the salt concentration is different for EAF and AEF. There fore, the nonequivalence cannot be accounted for by only the electrostatic effect, suggesting that it originates from some intrinsic property of the α-helix.

Notes: Using quasielastic light scattering, we have determined the diffusion coefficients of low-density lipoprotein (LDL) and polystyrene latex spheres over the temperature range of 293-318 K. The results show that after correction for thermal changes in the solvent, there remains a residual negative temperature coefficient in the diffusion amounting to about -0.6%/K that is independent of the chemical type of complex. Confirmation of these results was obtained for LDL through sedimentation studies over a similar range of temperatures. The residual temperature coefficient was similar to that reported for oxyhemoglobin [W. B. Veldkamp and R. Votano (1980) Biopolymers 19, 111-124] and greater than that found for bovine serum albumin by these and earlier workers. These observations show that the residual dependence on temperature is not an isolated phenomenon and could in part be explained by increased aggregation of particles, although this is not the primary cause of the effect.

Notes: The conformational changes of poly(dA-dT) from random coil to ordered structure with stacked bases produce important changes in the Raman line intensities (hypochromism) when the polymer is excited under the preresonance Raman conditions (λ excitation = 300 nm). Poly(dA-dT)-RNase and poly(dA-dT)-histone H1 interactions have been studied as models of mechanisms of destabilization and stabilization by proteins of the DNA secondary structure, respectively, following this intense preresonance Raman hypochromism. In addition, the specific variation of the intensity of the 1582-cm-1 line of adenine is interpreted in terms of the interaction of the amino group with the RNase (thus involving the large groove). In the poly(dA-dT)-H1 complex, the intensity of the 1665-cm-1 line of thymine increases. This increase appears to involve the C2=O group of thymine, located in the narrow groove.

Notes: The enthalpies of binding of chloroquine and quinacrine to DNA at different molar ratios of drug to DNA and at different ionic strengths have been measured. The limiting values obtained with quinacrine fall in the range found for typical intercalating agents (e.g., ethidium, proflavin, adriamycin), whereas the value obtained with chloroquine is always zero, independent of the ratio of drug to DNA and ionic strength. The dilatometric measurements performed on the same systems and on the ethidium-DNA system show that when ethidium and quinacrine bind to DNA at low drug/DNA ratios, a volume decrease of about 16 mL/mol of bound drug occurs. No change in volume is observed when the two drugs bind to DNA through external, electrostatic forces. The volume change can be attributed to the loss of structured water around hydrophobic moieties of the drug molecules, following intercalation. In contrast, chloroquine binding to DNA at low drug/DNA ratios is characterized by a volume change distinctly smaller than that shown by quinacrine. The low ΔVB and ΔHB values shown by chloroquine are discussed in terms of the mechanism of interaction with DNA.

Notes: The conformation and the dynamic structure of single-stranded poly(U) and poly(C) in neutral aqueous solution have been investigated by 1H-nmr at two different frequencies (90 and 250 MHz) and at various temperatures. Measurements of proton chemical shifts, coupling constants JH-H, and proton relaxation times, T1, T2, versus temperature show a striking difference in conformation and in dynamic structure between the two polynucleotides studied. The temperature effect on δ and JH-H is found to be substantial for poly(C) and insignificant for poly(U). The S conformer is favored in poly(U), whereas the N conformer strongly predominates in poly(C) (≃90%), similar to the case for RNAs. These results suggest that single-stranded poly(C) probably possesses a helical or partial helical structure, whereas poly(U) shows a clear preference for the random coil, in agreement with the optical results. The local motions of the ribose and base were studied at various temperatures by measurements on the relaxation times at 90 and 250 MHz. For a given temperature between 22 and 72°C, the ratio T1(90)/T1(250) is practically the same for all poly(U) protons, indicating that in this temperature interval the ribose base unit of poly(U) undergoes an isotropic motion characterized by a single correlation time τc. Above 52°C, poly(C) exhibits a dynamic structure similar to poly(U). Below this temperature, poly(C) exists in an equilibrium between randomly coiled and single-stranded helix forms. This situation is characterized by a strong cross-relaxation effect and T1 values corresponding to a relatively short apparent correlation time. An activation energy of 4 kcal/mol was determined for the motion of the ribose-base unit in both single-stranded polynucleotides.

Notes: The complexes of the three BrCN-cleaved fragments of sperm whale apomyoglobin with hemin were studied by circular dichroism (CD). In native myoglobin, the heme is located in the middle fragment; the isolated peptide (residues 56-131), however, produces little extrinsic Cotton effects by the addition of hemin, although about four molecules of hemin are bound to this peptide. In marked contrast, the COOH-terminal peptide (residues 132-153), which binds three hemin molecules, shows strong Cotton effects in the Soret bands and drastically changes its conformation from unordered to highly helical. The Arg-modified or Lys-deaminated peptide no longer undergoes conformational changes by the addition of hemin, suggesting that the two propionic acid groups of one hemin molecule interact with the Arg residue and one of the Lys residues, which stabilizes the induced helical conformation. The NH2-terminal peptide (residues 1-55) binds one hemin molecules, and the helicity of this fragment is slightly enhanced by the addition of hemin. Both the CD and difference absorption spectra indicate that the mode of interaction between the peptides and hemin are different for the three apomyoglobin fragments.

Notes: CD study of four modified nucleosides, constituents of tRNA molecules, revealed that 2-thio-5-methyluridine and 5-methyluridine in aqueous solution, 0.1N HCl, and organic solvents essentially occur in an anti-conformation. 5-Methylcytidine also occurs in an anti-conformation similar to cytidine in aqueous solution and organic solvents, while 2-thiocytidine dihydrate appears to occur in an anti-conformation. It is stressed that the CD data of thionucleosides might be applied to the successfully conformational analysis of tRNA molecules.

Notes: It has been inferred from previous studies that Mn2+ ions bind preferentially to G·C base pairs in DNA, and it has even been suggested that this preference for G·C pairs might be responsible for some of the Mn2+ specific effects observed in various biochemical reactions. In this paper we investigate the AT/GC preference of Mn2+ by direct competition studies in which AT-rich DNA was dialyzed against GC-rich DNA in the presence of varying amounts of Mn2+. Analysis of these results demonstrates that over a wide range of Mn2+/DNA(P) molar ratios, Mn2+ binds to A·T and to G·C base pairs with virtually identical affinity, although in a somewhat different mode. Both the present and previous nmr, uv, CD, and melting studies are discussed in terms of the different modes of binding of Mn2+ to single- and double-stranded DNA.

Notes: We have determined extinction angles and flow birefringence of T7 bacteriophage DNA over a wide range of shear, polymer concentration, and solvent ionic strength. From these data, information on the simple salt dependence of coil permeability to solvent and on short-range intrachain interactions (persistence length) was obtained. At all ionic strengths, our results are consistent with a partially draining coil in the Gaussian subchain dynamical theory of Rouse-Zimm-Tschoegl-Bloomfield. Salt dependence of persistence length is comparable to, although somewhat less than, that obtained previously using similar methods with a fivefold higher-molecular-weight DNA (T2 bacteriophage DNA). Possible reasons for observed discrepancies are analyzed, and the results of this work are compared in detail to other current studies of solvent ionic strength dependence in persistence length and hydrodynamic properties of DNA.

Notes: Variation of collagen fibril structure in tendon was investigated by x-ray diffraction. Anatomically distinct tendons from single species, as well as tendons from different species, were examined to determine the variations that exist in both the axial and lateral structure of the collagen fibrils. The meridional diffraction is derived from the axial collagen fibril structure. Anatomically distinct tendons of a particular species give meridional patterns that are indistinguishable within experimental error. The meridional diffraction patterns from tendons of different mammals are similar but show small species-specific variations, most noticeably in the 14th-18th orders. Tendons of birds also give meridional patterns that are similar to each other, but the avian patterns differ considerably from the mammalian ones. Avian tendons give stronger odd and weaker even low orders, a feature consistent with a reduced gap:overlap ratio, and have a distinctive intensity pattern for the higher meridional orders. Interpretation of these differences has been approached using biochemical data, diffraction by reconsituted fibers of purified collagen, and Fourier transform analysis. From these methods, it appears that the variations observed in the lower orders (2nd-8th) and in the higher orders (29th-52nd) are probably related to differences in the primary structure of the Type I collagen found in the different species. The variations observed in the 14th-18th orders appear not to be related to features within the triple-helical domain of the molecule.Equatorial diffraction yields information on the lateral packing of collagen molecules in the fibrils, and considerable variation was seen in different tendons. Rat tail tendon gives sharp Bragg reflections, demonstrating the presence of a crystalline lateral arrangement of molecules in the fibril. For the first time, sharp lattice reflections similar to those in rat tail tendon have been observed in nontail tendons, including rat achilles tendon, rabbit leg tendon, and wing and leg tendons of quail. In the rabbit and quail tendons, one of the strong equatorial reflections characteristic of the rat tendon pattern, at 1.26 nm, was absent. The positions of the equatorial maxima, which are a measure of intermolecular spacing, varied considerably, being smallest in the specimens displaying crystalline packing. The intermolecular distance in chiken and turkey leg tendons is longer than that found in mammalian tendons, or in avian wing tendons, which supports the hypothesis that a larger intermolecular spacing is characteristic of tendons that calcify.Thus, x-ray diffraction indicates there are reproducible differences in both the axial and lateral structure of collagen fibrils among different tendons. This work on tendon, a tissue containing almost exclusively Type I collagen as its major component, should serve as a basis for analyzing the structure of other connective tissues, which contain different genetic types of collagen and larger amounts of noncollagenous components.

Notes: The conformation of poly(α-L-aspartic acid) was investigated on a sample in which β-bonds were not detected. CD and ir spectroscopy showed that poly(α-L-aspartic acid) passes through a conformational change induced by changes of the degree of ionization that is accompanied by precipitation; the precipitate is probably highly helical. The change was also detected by potentiometric titration.

Notes: We studied the kinetics of the heat denaturation (at 50°C) of met-hemoglobin in the presence of various monohydric alcohols. The denaturation rate was slowed by the presence of small concentrations of methanol and ethanol; in all the other cases, i.e., at high concentrations of methanol and ethanol, and in the whole concentration range studied for iso- and n-propanol, an increase in the denaturation rate was observed. Following a procedure already applied to the study of the effects of the same alcohols on the reaction of hemoglobin with oxygen, we separated the overall observed effects into contributions related to the variation of the bulk dielectric constant of the medium (bulk-electrostatic contributions) and contributions not related to variations in this parameter (nonbulk-electrostatic contributions). For all the alcohols, we found a unique correlation law connecting the above nonbulk-electrostatic contributions with the analogous ones previously reported for the T → R transition of hemoglobin. This fact strongly supports the validity of the procedure used and suggests that nonbulk-electrostatic contributions, relative to these two different processes, have a common background and are univocally determined by the extent of the “solvent perturbation” imposed by the presence of the perturbing cosolvents.

Notes: 2,2,′,2″,2‴-Tetrapyridineiron(III) complex ions anchored to poly(L-glutamate) (FeL) or poly(D-glutamate) (FeD) were used as catalysts for the H2O2 oxidation of L(+)-ascorbic acid at pH 7 and varying complex:polymer-residue molar ratios [C]/[P]. Evidence is produced that the reaction is a composite process reflecting contributions from parallel pathways, one of which corresponds to a catalytic route and is [H2O2]-independent and the other to an uncatalyzed electron-transfer process between the ascorbate anion and hydrogen peroxide. Stereospecific effects in the catalysis are observed on increasing the complex:polymer ratio, which corresponds to an increase of the amount of α-helical fraction in the polypeptide supports (xa). Thus, at [C]/[P] = 0.01 (xa 〈 0.05), kFeD/kFeL = 1.0; but at [C]/[P] = 0.20 (xa ≈ 0.70), kFeD/kFeL = 4.0 ± 0.5, kFeD and kFeL being the second-order rate constants of the electron-transfer reaction between the FeD or FeL isomer of the asymmetric catalyst and the L-ascorbate anion. The activation energies were found to increase markedly on going from the former to the latter complex:polymer ratio but, at the same time, to exhibit equal values with both enantiomeric catalysts. Stereoselectivity therefore appears to be an entropy-controlled process, arising from the conformational rigidity of the precursor complex, which very likely sees the substrate molecules bound to the chiral residues of the ordered polymer surrounding the active sites. The implications of the stereochemical features of the substrate-catalyst adduct on the mechanism of electron transfer are also discussed. Evidence is presented that the asymmetric [Fe(tetpy)(OH)2]+-polyelectrolyte systems play the additional role of environmental controller of the uncatalyzed oxidation of the L-ascorbate anion.

Notes: A temperature-jump relaxation study of the interaction of tilorone with different polynucleotides and DNA has been performed. A single relaxation time, attributed to the intercalation step, has been observed in the case of poly[d(A-T)]·poly[d(A-T)], poly[d(A-C)]·poly[d(G-T)], poly[d(G-C)]·poly[d(G-C)], and poly(dG)·poly(dC). No intercalation into poly(dA)·poly(dT) occurs, and the interaction with poly(dG)·poly(dC) is different from what is observed with the other intercalating homopolymers. Refinement of the binding model is suggested from the analysis of the kinetic data. The relaxation curves obtained with DNA are well simulated based on a binding mechanism where DNA is considered a heterogeneous lattice and each type of site behaves as if it were located in the corresponding homopolymer. Poly(dA)·poly(dT) shows a unique behavior: studies of the effects of concentration and temperature indicate that tilorone acts as a probe of a process involving the polynucleotide alone. This process appears to be related to the dynamic structure of the nucleic acid and is detectable only when the bound dye is not intercalated.

Notes: We had earlier observed that the detailed nature of the β-structure adopted by poly(L-tyrosine) depends on molecular weight [Auer, H. E. & McKnight, R. P. (1978) Biochemistry 17, 2798-2805]. It was proposed that shorter molecules form an open, single-layered sheet (class I) and that longer chains fold over to generate at least two layers (class II). In this work, solvent perturbation difference spectroscopy of the chromophoric side chain was applied to gain additional support for the model. Two sample-reference pairs of media, sodium acetate vs sodium chloride and urea vs buffer, were studied. Great care was taken to achieve identical conditions in the sample and reference cells. The factors of importance in executing the experiments are the polypeptide concentration, the degree of side-chain ionization, achievement of the same class of β-conformation, and the absence of significant aggregation. Difference spectra obtained with both solvent pairs have similar features. Low-molecular-weight samples manifest difference bands arising from both ionized and neutral tyrosine side chains, while high-molecular-weight samples yield spectra with contributions primarily from ionized residues. The interpretation of these results is that the class I particle has both ionized and neutral residues exposed to the solvent medium, whereas the class II particle is folded, with neutral residues restricted to the interior of the fold and primarily ionized residues on the outer surfaces exposed to the solvent. Our results, therefore, corroborate the original model.

Notes: Extinction angles, flow birefringence, and intrinsic viscosities are compared for linear, bihelical DNAs from viral and other sources that span a range in molecular weight from ∼105 to 1.3 × 108. This range effectively spans the region over which transition from rigid-rod to expanded-coil hydrodynamic property behavior occurs. All DNAs are in identical, phosphate-EDTA, neutral-pH buffers, 0.1M in NaCl. The extinction angle is a hydrodynamic property only and is thus particularly sensitive to effects of kinetic chain rigidity or internal viscosity. Our extinction angle results cannot be interpreted by any simple, single-function theoretical expression. Rather, they must be divided into distinct high- and low-molecular-weight domains. The low-molecular-weight region is typical of rigid-particle opticohydrodynamic property behaviour characterized primarily by particle orientation. The high-molecular-weight domain shows evidence for a finite internal viscosity effect, however, which can be interpreted as very nearly Kuhnian using Cerf's amplification of the Gaussian subchain model to include internal viscosity. It is found that the high-molecular-weight, monodisperse viral DNAs from T7, T5, and T2 bacteriophage show an internal viscosity contribution to the limiting extinction angle-shear rate ratio of ∼3 × 10-3 s. An effect of this magnitude may be marginally important in interpreting extinction angle and certain other hydrodynamic property data for high-molecular-weight DNA systems. Internal viscosity effects do not appear to be manifest in the ratio of flow birefringence to intrinsic viscosity, however, and the persistence length of the high-molecular-weight DNAs is found to be independent of molecular weight to within estimated experimental uncertainty.

Notes: Phosphorylase kinase contains four approximately equivalent binding sites for 1-anilinonaphthalene-8-sulfonate (1,8-ANS). Measurements of the time decay of fluorescence anisotropy have failed to give any indication of internal degrees of rotational freedom involving a significant portion of the tertiary structure. In the presence of 1 mM Ca2+, calmodulin binds one molecule of 1,8-ANS. No binding occurs in the absence of Ca2+. The binding is strongly temperature-dependent, a decrease in binding occurring with increasing temperature. Determinations of the time decay of fluorescence anisotropy indicate the presence of internal rotations, which become more important with increasing temperature. Complex formation between phosphorylase kinase and calmodulin reduces the binding of 1,8-ANS.

Notes: The dissociation of beef liver and bacterial (Micrococcus lysodeikticus) catalases by the action of sodium n-dodecyl sulfate (SDS) has been investigated as a function of SDS concetration and time by ultracentrifugation. The rate of dissociation of beef liver catalase is found to be much faster than that for bacterial catalase in 25 mM SDS at pH 7.0. Beef liver catalase is dissociated into its four subunits after 24 h, whereas bacterial catalase is not completely dissociated after 36 days of incubation. The binding of SDS to beef liver catalase obeys a Hill equation with a cooperativity exponent of 2.0 and a binding constant of 440. The initial interaction of SDS with beef liver catalase can be detected by microcalorimetry, whereas the mixing of SDS with bacterial catalase is athermal. Bacterial catalase retains enzymic activity in the presence of SDS, whereas beef liver catalase is completely deactivated at SDS concentrations above 5 mM. Beef liver catalase is more sensitive to acid denaturation than bacterial catalase, and the rate of dissociation for both catalases is sixth-order in proton concentration. Comparison of the amino acid analysis of the two catalases shows that bacterial catalase has a smaller number of lysyl residues and a larger number of glutamyl residues than beef liver catalase. Taken together these structural differences could lead to a reduced affinity of bacterial catalase for the binding of SDS as observed.

Notes: m-Dinitro-benzol und einige seiner Derivate (I, II, VII) lassen sich durch aufein-anderfolgende Einwirkung von Alkylmagnesiumhalogeniden, Methylamin/Formaldehyd und Essigsäure zu Mannich-Verbindungen von Dinitrodialkylcyclohexenen (Vb-e, VIII) umsetzen.

Notes: 3-Brom-cyclo-penten,-hexen und-hepten reagieren mit Lithiumaluminiumhydrid unter Bildung der jeweiligen cyclischen Monoolefine. Ann substituierten 3-Brom-cyclohexenen wurde gezeigt, daß die Reaktion sowohl als einfache nucleophile Substitution des Broms durch Wasserstoff als auch unter Allylumlagerung mit Angriff des Hydridions am C-Atom 1 verläuft. Die in beiden Allylstellungen bromierten cyclischen Olefine reagieren mit Lithiumaluminiumhydrid unter Bildung mehrerer Produkte, die durch Angriff des Hydrids an einem halogentragenden C-Atom (a), an einem olefinischen C-Atom (b) und an einem Brom-atom (c) entstanden sind. Reaktion (a) liefert Monoolefin, (b) ergibt 4-Bromolefin und nach (c) entsteht 1.3-Diolefin. Die Eliminierung nach (c) wurde allerdings nur am unsubstituierten Cyclohexen- und Cycloheptendibromid beobachtet. Für die Eliminierung wird ein weitgehend koplanarer Übergangszustand angenommen, der bei den anderen untersuchten Dibromiden nicht möglich ist.

Notes: Die Desaminierung des 9-Amino-Δ4(10)-octalins in essigsaurer Lösung gibt zu etwa 80% die substituierten Allylalkohole Δ9(10)-Octalol-(1) und Δ4(10)-Octalol-(9) nebst Acetat, sowie die aus diesen durch normale Wasserabspaltung hervorgehenden Hexaline.

Notes: Bei der Umsetzung von β-Phenäthylmercaptan mit Aldehyden und Chlorwasserstoff entstehen [α-Chlor-alkyl]- β-phenäthyl-sulfide, die mit Aluminium-chlorid unter Ringschluß zu Isothiochromanen reagieren. - 1-Chlor-isothio-chroman, durch Einwirkung von Chlor auf Isothiochroman gewonnen, liefert mit Alkyl- oder Arylmagnesiumhalogeniden 1-Alkyl- bzw. 1-Aryl-isothiochromane, mit Mercaptanen 1-Alkylmercapto-, mit sekundären Aminen 1-Di-alkylamino- und mit Alkoholen 1-Alkoxy-isothiochromane. - Durch Umsetzung der letzteren mit Natriumhydrogensulfit entsteht Isothiochroman-sulfonsäure-(1), die in Isothiochroman-S-dioxid-sulfonsäure-(1) bzw. deren Ester übergeführt werden kann.

Notes: 1.2-Benzpyren gibt der Bromierung das 5.8-Dibromderivat II und bei der Chlorierung das 3.5.8.10-Tetrachlorderivat V. Aus II wird das 5.8-Dinitril III und daraus die entsprechende Dicarbonsäure IV dargestellt. Die Hydrierung des 1.2-Benzpyrens führt zunächst zu einer Hexahydroverbindung, die ein Anthracenderivat ist, und dann zu dem Decahydro-1.2-benzpyren VI, das einen Naphthalinkern enthält. Die Oxydation verläft sehr komplex und liefert neben dunklen Kondensationsprodukten nur geringe Mengen zweier Säuren, die bei der Decarboxylierung Phenanthren und Triphenylen geben. - 3.4-Benzpyren liefert unter milden Bedingungen das 5-Brom-Derivat VII. Weitere Chlorierung von Trichlor-3.4-benzpyren VIII führt zum Trichlor-3.4-benzpyren-tetrachlorid IX.

Notes: Die Produkte des Zerfalls der 1.2-Benzo-cyclenyl-(4)-diazonium-lonen (II) in Essigsäure werden mit denen der Acetolyse der 1.2-Benzo-cyclenyl-(4)-tosylate (VI) verglichen. Die erste Reaktion vollzieht sich am Beispiel des Vertreters mit 7-gliedrigem Ring mit 53-proz., die zweite mit 89-proz. Konfigurationserhaltung.

Notes: Thioschwefelsäure läß sich mit Thionylchlorid in guten Ausbeuten unter Chlorwasserstoffabspaltung zu einem äquimolaren Gemisch aus Disulfan-disulfonsäure und Trisulfan-disulfonsäure oxydieren. Mit Sulfurylchlorid bildet H2S2O3 neben HCI und Schwefeldioxid reine H2S4O6.

Notes: 4.5.8-Trihydroxy-6-mercapto-chinolin-carbonsäure-(2) (II) wird durch Spaltung des Xanthogenats XV mit Aluminiumbromid dargestellt. Die Spaltung von XV mit Bromwasserstoffsäure führt zur reduktiven Abspaltung der Schwefelfunktion. Bei der Methylierung von II mit Diazomethan entsteht neben dem vollmethylierten Chinolinderivat XXI ein Chinolon XXII, bei dem die zur Chinolon-Carbonylgruppe peri-ständige 5-Hydroxygruppe unmethyliert bleibt. II ist wider Erwarten nicht identisch mit einem aus dem Ommochrom „Ommin A“ dargestellten Abbauprodukt.

Notes: Bei der Oxydation von Pyrogallol in alkoholischer Lösung wird Purpurogallincarbonsäure-(9)-ester gebildet, dessen Konstitution sich aus dem Abbau zu Purpurogallin und Methylterephthalsäure ergibt.

Notes: 1′.2′-Dihydroxy-benzotropolon-Derivate können nach zwei Methoden dargestellt werden: 1.aus 3 Moll. eines o-Benzochinons mit unsubstituierter Doppelbindung und 1 Mol. eines geeigneten Pyrogallolderivates, 2. durch Oxydation eines Gemisches geeigneter Brenzcatechin- und Pyrogallolderivate mit KJO3 bzw. K3[Fe(CN)6]. Bei der Umsetzung von o-Benzochinonen mit 4-Methylpyrogallol wird nur dasjenige Isomere (I a) gebildet, bei welchem die Reaktionspartner im Orientierungskomplex die räumlich günstigste Anordnung (Methylgruppe auf der von der Verknüpfungsstelle abgewandten Seite) haben. Zwei Synthesen für Trimethylpyrogallol und die Darstellung von 2′-Hydroxy-benzotropolon-chinon-(1′.4′) (VIII) werden beschrieben.

Notes: symm. Tetra-pyrenyl-(3)-äthan (III), symm. Di-pyrenyl-(3)-diphenyl-äthan (VII), 2.3-Di-[pyrenyl-(3)]-butan (IX), 2.2.5.5-Tetramethyl-3.4-diphenyl-3.4-di-[pyrenyl-(3)]-hexan (X) und Hexa-pyrenyl-(3)-äthan (XI) wurden dargestellt und ihre Fähigkeit zur Dissoziation in Radikale bei Raumtemperatur mit Hilfe der Elektronenspinreasonanz -Method (ESR) untersucht. Mit Ausnahme von 2.3-Di-[pyrenyl-(3)]-butan sind sämtliche der untersuchten Verbindungen bei Raumtemperatur partiell, das Hexa-[pyrenyl-(3)]-äthan erwartungsgemäß quantitativ dissoziiert. Beim symm. Tetra-α-naphthyl-äthan (VIII) ist dagegen keine Radikaldissoziation nachweisbar. - Das von Pyren ausgehend in guter Ausbeute in zweistufiger Synthese darstellbare symm. Tetra-pyrenyl-(3)-äthan ist im organischen Solvens bei Raumtemperatur unlöslich. Es ist im festen Zustand zu 0.0025% in Radikale dissoziiert. - Die Abhängigkeit der Carbonylfrequenz im IR-Spektrum von Mono- und Diarylderivaten des Formaldehyds vom Kondensationsgrad des Arylrestes wurde untersucht.

Notes: 3-Halogen-pyridazine reagieren mit Anthranilsäure oder Anthranilsäure-äthyl-ester zu Pyridazino[3.2-b ]chinazolonen-(10), deren Eigenschaften beschrieben werden.

Notes: Bei Eliminierung des Chlors aus cis-3.4-Dichlor-cyclobuten mittels Natriumamalgam in äther. Lösung entsteht das syn-Tricyclo[4.2.0.02.5]octadien-(3.7) (I), identisch mit dem früher aus 1.2.3.4-Tetrabrom-cyclobutan erhaltenen Produkt. Bei ähnlicher Behandlung mit Lithiumamalgam bildet sich überwiegend das isomere anti- Tricycloocatadien (II). Die Ozonspaltung und einige Derivate dieser Kohlenwasserstoffe werden beschrieben.

Notes: Die Umsetzung von L-Tryptophan mit D-Fructose liefert kristallisierte 2-Nα-L-Tryptophan-2-desoxy-D-glucose(I), mit D-Glucose 1-Nα-L-Tryptophan-1-desoxy-D-fructose (II), Aus L-Histidin und D-Fructose entsteht 2-Nα-L-Histidin-2-desoxy-D-Glucose (II).

Notes: Bei der Umsetzung der Hexacarbonyle der Chromgruppe mit Bipyridyl-(2.2′) bzw. 1.10-Phenanthrolin geht die Substitution über die Tetracarbonylstufen M(CO)4bipy bzw. M(CO)4phen hinaus, wenn man in hochsiedenden Kohlenwasserstoffen, wie Decalin, Tetralin oder 1-Methyl-naphthalin arbeitet. Während mit Mo(CO6 und W(CO)6 die Dicarbonylverbindungen M(CO)2bipy2 bzw. M(CO)2phen2 gebildet werden, entstehen mit Cr(CO)6 die totalsubstituierten Typen Cr(bipy)3 und Cr(phen)3.

Notes: Die Hexacarbonyle M(CO)6 (M=Cr, Mo, W) setzen sich bei 120° mit flüssigem NH3 zu den Tricarbonyltriamminverbindungen M(CO)3(NH3)3 um; nur beim Cr(CO) 6 ist bei 80° auch Cr(CO)5NH3 zugänglich. Bei den Reaktionen von M(CO)4bipy und M(CO)4phen (bipy = Bipyridyl-(2.2′), phen = 1.10-Phenanthrolin) mit flüssigem NH3 erfolgt bei 120° Substitution einer CO-Molekel unter Bildung der Verbindungstypen M(CO)3 bipyNH3 bzw. M(CO)3phenNH3. Bei den Umsetzungen von M(CO)4bipy mit Kaliumcyanid in flüssigem NH3 wird bei 60° bipy vollständig durch CN⊖ ersetzt. Hierbei werden mit Cr(CO)4bipy K2[Cr0(CO) 4(CN)2], mit Mo(CO)4bipy und W(CO)4bipy unter gleichzeitiger CO-Substitution K3[M0(CO) 3(CN)3] gebildet.

Notes: Aryl- und Alkylisocyanate reagieren mit Benzolderivaten unter Friedel-Crafts-Bedingungen zu N-substituierten Benzoesäureamiden. Auch die wenig reaktionsfähigen Halogenbenzole sind der Umsetzung zugänglich.

Notes: Das kürzlich als 2-Hydroxy-4.5-epoxy-6-O-methyl-tetrahydro-apogalanthamin beschriebene Abbauprodukt aus Galanthamin wurde als (-)-Epigalanthamin identifiziert.

Notes: Wegen der zentralen Stellung der Chinonmethide in der Chemie des Lignins wurden 3 niedermolekulare p-Chinonmethide auf ihre chemischen Reaktionen und ihre Polymerisation untersucht. Die Polymerisate sind zur monomeren Stufe abzubauen und bestehen aus fortlaufend verätherten p-Hydroxy- benzyl-alkoholen (Polybenzylaryläthern) vom Typus XX.

Notes: Die cis-Formen geometrischer Isomerenpaare scheinen ganz allgemein energie ärmer zu sein, wenn nicht H-H-Wechselwirkung oder extreme Raumbeanspruchung wie beim 1.2-Dijod-äthylen vorliegen. Die Isolierung der geometrischen Isomeren der im Titel genannten Verbindungen erlaubt deren Strukturzuordnung und die Untersuchung der thermischen Gleichgewichte. Die cis-cis-Isomeren sind in Benzollösung energetisch gegenüber den trans-trans-Isomeren stark bevorzugt, welche bei den Meßtemperaturen von 100° und 150° nur zu 10 bis 15% im Gleichgewicht vertreten sind.

Notes: Messungen der Optischen Rotationsdispersion und des Zirkulardichroismus von N-Phthalyl-aminen beweisen die Existenz von mindestens einer optischaktiven Absorptionsbande im Bereich oberhalb von 300 mμ, die im UV-Spektrum nicht erkennbar ist. Aus dem Vorzeichen der zugehörigen Cotton-Effekt-Kurve kann die absolute Konfiguration bestimmt werden: N-Phthalyl-Derivate optisch-aktiver Amine der (R)-Reihe zeigen einen negativen Cotton-Effekt, solche der (S)-Reihe einen positiven. Entsprechende Messungen an N-Phthalyl-Derivaten von α-Aminosäuren führten zum Nachweis von mindestens zwei optischaktiven Absorptionsbanden, die wiederum im UV-Spektrum nicht erkennbar sind. Die vorliegende Untersuchung stellt ein weiteres Beispiel dar für die Anwendung der Optischen Rotationsdispersion und besonders des Zirkulardichroismus zur Ermittlung verdeckter Absorptionsbanden.

Notes: Bei Versuchen, Cyanformaldehyd herzustellen, wurden bei Raumtemperatur nur Cyanwasserstoff und Kohlenmonoxyd bzw. Ameisensäure erhalten. Dagegen konnten das Oxim und Phenylhydrazon des Cyanformaldehyds, beide in syn- und anti- Form, dargestellt werden. Das Cyanformaldoxim ist extrem unbeständig gegen Basen, die den exothermen Zerfall in Dicyan und Wasser katalysieren. Das Oxim und Phenylhydrazon sowie geeignete Derivate konnten nicht zu Abkömmlingen des s-Triazin-trialdehyds trimerisiert werden.

Notes: Für die im Teak aufgefundenen Verbindungen Tectol (C30H26O4, I) und Dehydrotectol (C30H24O4, V) konnte die Konstitution durch Abbau, Reaktion mit Acetylendicarbonsäure-dimethylester, Überführung ineinander sowie durch die Synthese des Tetrahydrotectols (IX), Tectols und Dehydrotectols festgelegt werden. V dürfte das erste in der Natur aufgefundene tieffarbige Dehydrodinaphthol sein. Da es in festem Zustande ein schwaches ESR-Signal gibt, liegt es wohl teilweise als Radikal XIII vor. Ein Cyclisierungsprodukt X aus Tectol und andere Verbindungen aus Teak werden beschrieben.

Notes: Es wird über die Spaltung der Schwefel-Stickstoff-Bindung der Verbindungen CH3SNR2 (R = (CH3, C2H5), [(CH3)2N]2SO durch Borchloride berichtet.

Notes: Oson-1-hydrazone und Osazone, die nur asymmetrisch disubstituierte Hydrazinreste enthalten, reagieren mit Hydroxylamin unter Bildung von Oson-1-hydrazon-2-oximen. Mit primären Hydrazinen lassen sich daraus Mischosazone herstellen. Vergleichend wird über entsprechende Derivate des Methylglyoxals berichtet.

Notes: Einige aliphatische Diazoverbindungen - hauptsächlich aus der Reihe des Diazocyclopentadiens und der Bis-alkyl- bzw. Bis-arylsulfon-diazomethane - mit zum Teil recht hoher Säurestabilität werden dargestellt. Die der NN-Schwingung zuzuordnende Infrarotabsorption im Wellenzahlenbereich um 21OO/cm verschiebt sich mit zunehmender Säurestabilität nach höheren Frequenzen.

Notes: Triphenylphosphin sowie Phenyl-biphenylen-phosphin wurden durch Umsetzung mit Phenylazid und anschließend Methylbromid in die zugehörigen Iminiumbromide I und III übergeführt, die sich bei Einwirkung von Lithiumarylen zu pentaarylierten Phosphoranen abwandeln ließen. Nach diesem neuen Verfahren konnten außer Pentaphenylphosphoran die analogen Verbindungen IV, V und XI präpariert werden.

Notes: Drei Vertreter der im Tribus Anthemideae L. Weit verbreiteten Enolätherspiroketale werden synthetisiert. Die als Recemate erhaltenen Enoläther stimmen IR-spektroskopische mit den Naturstoffen überein. Eine weitere Verbindung, die erstmals von N. A. SÖRENSEN isoliert worden ist, wird in ihrer Struktur durch Synthese gesichert.

Notes: Alkaliphosphide vom Typ MePHR (R = C6H5, c-C6H11; Me = Na, K) reagieren mit Kohlendioxid bzw. Chlorameisensäure-äthylester unter Metall-Wasserstoff- Austausch über die Zwischenprodukte MeP(R)CO2 Me bzw. MeP(R)CO2C2H5 zu prim. Phosphinen und Organophosphin-P.P-bis-carboxylaten bzw. -[carbonsäure-äthylestern] RP(CO2Me)2 bzw. RP(CO2C bzw. RP(CO2 C2H5)2. - Im Gegensatz zu den nicht existenten Säuren RP(CO2H)2 (Zerfall in CO2 und RPH2) sind die Ester RP(CO2C2H5)2 relativ luftbeständige, destillierbare Flüssigkeiten.

Notes: Durch Umsetzung des Pseudoalkalisilanolats Heptamethylstibinosiloxan mit Tris-trimethylsiloxy-aluminium, -gallium und -eisen entstehen spontan und quantitativ wohlkristallisierte, neuartige Tetramethylstibonium-tetrakis- trimethylsiloxy-metallate des Typs [(CH3)4Sb]⊕{Al, Ga, Fe[OSi(CH3)3]4}⊖. Physikalische und chemische Eigenschaften sowie IR- und NMR-spektroskopische Daten beweisen für diese Verbindungen eine ionische Struktur aus tetraedrischen Tetramethylstibonium-Kationen und Tetrakis-trimethylsiloxy-metallat-Anionen, die inzwischen auch durch Röntgenstrukturanalyse gesichert werden konnte. Die Struktur- und Bindungsverhältnisse werden an Hand der vorliegenden spektroskopischen und kristallographischen Daten diskutiert.

Notes: Aliphatische bzw. alicyclische α.β-und β-γ-ungesättigte Carbonsäureester liefern in Gegenwart von Co2(CO)8 als Katalysator mit Synthesegas bei 200-250β gesättigte mono- bzw. bicyclische Lactone. Bei längerkettigen α.β-ungesättigten Estern werden infolge Isomerisierung während der Reaktion neben γ- auch δ-Lactone erhalten.

Notes: Durch Umsetzung von Methylazid mit Antimon(V)-chlorid in Methylenchlorid wurde ein Addukt der Zusammensetzung H3CN3:SbCl5 erhalten, das unter der Einwirkung von trockenem Chlorwasserstoff in Methylenchlorid in ein stabiles Methylenimmonium-hexachloroantimonat(V) (V) überging. Bei Ersatz von Chlorwasserstoff durch Deuteriumchlorid entstand N-monodeuteriertes Methylenimmonium-hexachloroantimonat(V). Die IR-Spektren aller dargestellten Verbindungen wurden aufgenommen und zugeordnet.

Notes: Lignin nach Björkman wurde mit Methanol/Chlorwasserstoff und mit wäßrigem Schwefeldioxyd behandelt. Dabei vermehren sich die titrimetrisch ermittelten Phenolgruppen. Entsprechende Versuche wurden ausgeführt mit Modellsubstanzen und den als Zwischenprodukte der Ligninbildung erkannten β-γ-Diaryläthern des Guajacylglycerins. Etwa jede achte bis zehnte Einheit des Coniferenlignins besteht aus Guajacylglycerin, das am γ-Hydroxyl mit Arylgruppen veräthert ist. Die γ-Aryläther entstehen bei der Addition von Phenolen an Chinonmethide und bei der Polymerisation der Chinonmethide.

Notes: Die Reaktion von Oxalychlorid mit silyliertem 4.5-Diamino-uracil (I) führt unter Ringschluß zu 2.4.6.7-Tetrakis-trimethylsiloxy-pteridin (II); silylierte Aminopyrimidine ergeben unter diesen Bedingungen Purin-Derivate. Die besonders leicht alkylierbare Tetrakis-triäthylsilyl-harnsäure VI liefert bei Einwirkung von Dimethyl-bzw. Diäthylsulfat. oder Methyljodid fast quantitativ z. T. sonst nur schwer zugängliche Derivate wie 1.7.9-Trimethyl- (VIIa), 1.7.9-Triäthyl-(VIIb), 1.3.7.9-Tetramethyl- (VIIc) und 1-Methyl-harnsäure (XIII). Ebenso läßt sich silylierte Harnsäure VI gut in 3-Stellung glykosidieren. So konnten erstmals Harnsäure VI gut in 3-Stellung glykosidieren. So konnten erstmals Harnsäure-3-glucosid (XIXf), -3-ribopyranosid (XIXd) und -3-ribofuranosid (XIXe) erhalten werden. Letzteres ist mit dem in der Natur vorkommenden Ribosid identisch.

Notes: Aus Hydrazinhydrat bzw. Derivaten des Hydrazins und Isothiocyanato-essigsäure-äthylester werden Thiosemicarbazino-(4)-essigester dargestellt. Analog wie bei den Oligo-„[semicarbazino-[4]-essigsäuren]“ wird eine „Di-[thiosemicarbazino-(4)-essigsäure]“-Kette aufgebautExaktere Bezeichnungen wären hier zu unhandlich, vgl. 46. Mitteil., vorstehend. Es wird über einige Eigenschaften und Reaktionen der neuen Verbindungen berichtet. Außerdem werden IR-Spektren wiedergegeben und diskutiert.

Notes: Aus Cbo(Tosyl)-Hydrazinen und verschiedenen α-Isocyanato-fettsäure-äthylester werden α-[1-Acyl-semicarbazino-(4)]-fettsäure-äthylestern dargestellt. [1-Acyl-semicarbazino-(4)]-essigester wird in das Hydrazid übergeführt und erneut mit Isocyanato-essigester umgesetzt, wobei ein Stoff mit zwei aneinandergeknüpften Semicarbazino-(4)-acetyl-Resten erhalten wird. Diese Kettenverlängerung wird bis zum Acyl-„tetra-[semicarbazino-(4)-essigester]“Für die Bezeichnung der neuen Verbindungen werden hier häufig verschiedene Vorschläge gemacht. Exakte Namen werden für die einfacheren Verbindungen oder Verbindungstypen meistens nur einmal wiedergegeben, während bei einer wiederholten Erwähnung Vereinfachungen getroffen werden. Für die höhermolekularen stoffe muß wegen der Kompliziertheit auf eine korrekte Bezeichnung (ähnlich wie bei den Peptiden) ganz verzichtet werden) fortgeführt. Es werden einige Eigenschaften und IR-Spektren der auch als „Azapeptide“ aufzufassenden neuartigen Verbindungen diskutiert.

Notes: Die Pterine, die bei der Kondensation von 2.4.5.-Triamino-6-hydroxy-pyrimidin (I) mit Glucose bzw. Ribose mit oder ohne Hydrazinzusatz entstehen, wurden papierchromatographisch getrennt und weitgehend identifiziert. Es sind neben den 8/9-isomeren Tetra- und Trihydroxy-butyl-pterinen bzw. den Tri- und Dihydroxy-propyl-pterinen vor allem 8-Polyhydroxyalkyl-9-methyl-pterine und 9-Methyl-pterin.  -  Der komplizierte Reaktionsablauf und die Vielfalt der Reaktionsprodukte wird gedeutet.  -  Unter speziellen Bedingungen lassen sich vier Pterinderivate ohne schwierige Reinigungsoperationen isomerenfrei darstellen: 1. 9-[Tetrahydroxy-butyl]-pterin, 2. 8-[Tetrahydroxy-butyl]-pterin, 3. 8-[1′.2′-Dihydroxy-äthyl]-9-methyl-pterin und 4. 2-Acetamino-4-hydroxy-9-[3′.4′-diacetoxy-buten-(1′)-yl]-pteridin.  -  Bei der katalytischen Hydrierung von 9-Polyhydroxyalkyl-pterinen tritt eine stufenweise Eliminierung der Hydroxylgruppen der Seitenkette ein.

Notes: Das von MALKIN und NIERENSTEIN durch Einwirken von Zink/Acetanhydrid erhaltene vermeintliche Quercetylen ist kein Dimerisierungsprodukt, sondern Pentaacetoxy-flaven-(3). Ausgehend von Flavonolen über die Thioflavonole sind Quercetylen-decamethyläther und andere Biflavenylidene-(4) zugänglich, deren Struktur diskutiert wird.  -  Mit Ausnahme des Quercetylenäthers zeigen die Biflavenylidene Piezochromie und Piezomagnetismus.

Notes: Aus den Cycloadditionen der Nitrilimine an 14 Azomethine gehen 4.5-Dihydro-1.2.4-triazole in guter Ausbeute hervor. Diphenylnitrilimin lagert sich an die CN- und die CO-Doppelbindung der Arylisocyanate an, wobei 1.3-Diphenyl-4-aryl-1.2.4-triazolone-(5) und 2.4-Diphenyl-1.3.4-oxadiazolon-(5)-arylimide entstehen.

Notes: Aus Trichlorsilylgruppen enthaltenden Chlormethanen wurde mit Chlorwasserstoff in Gegenwart geringer Mengen Dimethylanilin eine dieser Gruppen als Siliciumtetrachlorid abgespalten: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Cl}_{\rm n} {\rm C}({\rm SiCl}_3)_{4 - {\rm n}} \, + \,{\rm HCL} \to \,{\rm SiCl}_4 \, + \,{\rm Cl}_{\rm n} {\rm CH}({\rm SiCl}_3)_{3 - {\rm n}} $$\end{document} Von den Entsprechenden methanen ging nur Tris-trichlorsilyl-methan diese Reaktionen ein. Das beschriebene Verfahren kann zur Aufklärung der Struktur dieser und ähnlicher Verbindungen dienen.

Notes: Aus Natriumcyanid mit 57.3% 13C wird über sechs Stufen in 25.6-proz. Ausbeute 1.4-13C-markiertes p-Benzochinon dargestellt.

Notes: Es wurden die kernmagnetischen 19F-Resonanzspektren flüssiger Mischungen aus SSF2 und FSSF untersucht, welche aus Kaliumfluorid und Dischwefel-dichlorid sowie Silberfluorid und Schwefel hergestellt worden waren. Die gefundenen chemischen Verschiebungen betragen, bezogen auf CFCl3, für SSF2 -79.5 ppm und für FSSF +122.5 ppm. Das Verfahren zur Gewinnung reinen Difluordisulfans, FSSF, aus Silberfluorid und Schwefel wird angegeben.

Notes: Das partiell durch N-tert.-Butyloxycarbonylgruppen (Abk. BOC) und tert.-Butylreste (Abk. t. Bu) geschützte β 1-23-Corticotropin-tyrosin23-amid wird nach dem Schema 10 + 13 mittels der Nitrophenylester- und der Carbodiimid-methode synthetisiert und durch Chromatographie an Sephadex®-G 25 angereichert. Das durch Abspalten der Schutzgruppen mit Trifluoressigsäure erhaltene Tricosapeptidamid-trifluoracetat wird durch Chromatographie an Carboxy-methylcellulose und durch kontinuierliche Hochspannungselektrophorese gereinigt. Die chromatographisch und elektrophoretisch einheitliche Verbindung zeigt im Sayers-Test an der Ratte bei intravenöser Applikation volle ACTH- Aktivität.

Notes: Die Reaktionsfähigkeit zahlreicher Carbonsäureamid-Komplexe gegenüber 4-Amino-1.3-dimethyl-uracil wird ermittelt.

Notes: Unter vergleichbaren Bedingungen wurden alle theoretisch möglichen n-Undecene bromiert bzw. hydrobromiert. Bei den cis- und trans-n-Undecenen besitzen alternierend jeweils die 3- und 5-Isomeren größere Reaktionsgeschwindigkeits-konstanten als die 2- und 4-Isomeren.

Notes: Die Kondensation von Chinacetophenon mit Benzaldehyd wird in Abhängigkeit von der Reaktionstemperatur und der Natur des Kondensationsmittels unter-sucht. Die gebildeten Kondensationsprodukte werden durch Derivate sowie spektral charakterisiert.

Notes: Die Umsetzung von wasserfreiem MnCl2 und CoCl2mit Chlornitrat oder Distickstoffpentoxid liefert die entsprechenden Nitrate als N2O4-Addukte, deren vorsichtige thermische Zersetzung die solvatfreien Nitrate Mn(NO3)2 und Co(NO3)2 entstehen läßt. Nach Debye-Scherrer-Aufnahmen sind die Nitrate isotyp. IR-Spektren und magnetische Messungen sprechen für rein ionogen aufgebaute Verbindungen. Dagegen müssen bei dem näher untersuchten Co(NO3)2.N2O4 nach Aussage des IR-Spektrums homöpolare Bindungsanteile diskutiert werden. Die Nitrate zersetzen sich bei 180° unter Abspaltung von NO2 und Sauerstoff, wobei die Oxide MnO1.655 und Co3O4 entstehen.

Notes: Die neun stellungs- und cis-trans-isomeren n-Undecene, von denen bisher nur n-Undecen-(1) und cis-n-Undecen-(5) in isomerenfreier Form bekannt waren, wurden erstmalig und in reiner Form hergestellt. Die physikalischen Konstanten der n-Undecene in Abhängigkeit von der Doppelbindungslage und der geometrischen Konfiguration wurden bestimmt. Die als Vorstufen für die Herstellung der n-Undecene benötigten n-Undecine wurden ebenfalls z. T. erstmalig synthetisiert und auf die gleiche Weise untersucht.