ALBERT

Notes: Poly-L-proline in the molecular weight range 50,000-90,000 has been synthesized from L-proline-N-carboxyanhydride. The molecular weight obtained is dependent on the initiator concentration. The rate constants for the polymerization have been determined by measuring the CO2 evolution. By observation of rotation during the polymerization, it is possible to deduce the conformation of the polymer in the polymerization solution. It is concluded that the immediate product of the polymerization is neither pure form I nor pure form II. The differences between form I and form II of poly-L-proline have been further characterized by measurements of their ultraviolet rotatory dispersion and their ultraviolet spectra.

Notes: The base-catalyzed hydrolysis rate of the cationic esters obtained by quaternization of N,N,N′,N′-tetramethylethylenediamine with phenylbromoacetate was studied in buffers and in solutions of partially neutralized polymeric acids. The polyanions were found to be powerful inhibitors of the reaction. This effect was interpreted as due to the association of the ester with the polyanion, from which the catalytically active hydroxyl groups are repelled. It is shown that kinetic data may be interpreted by a procedure similar to the Lineweaver-Burk plot to yield the reactivity of the bound ester and the dissociation constant of the polymer-ester complex.

Notes: A series of high molecular weight copolypeptides of L-proline and sarcosine have been synthesized. Experimental evidence is presented which indicates that the products are true copolymers rather than mixtures of homopolymers. In contrast to poly-L-proline I, a copolymer of L-proline-sarcosine I containing approximately 50% sarcosine is soluble in water. Two molecular conformations of the copolymers, similar to those found for polyproline, have been characterized by means of infrared spectroscopy and optical rotatory dispersion. The residue rotation of L-proline has been obtained from the copolymers and is -250°.

Notes: Investigations have been made on the optical rotatory dispersion properties of E. coli ribosomes and their constituent RNA and proteins. The results indicate that (1) no conformational changes are involved in the formation of a 70S particle from the 50S and 308 subunits, (2) the E. coli ribosomal proteins are similar to most globular proteins with little α-helix content, and (3) the conformation of RNA and proteins inside the ribosome is very similar to that in the free state.

Notes: The iodine which is added to an aqueous amylose solution is bound only partly by the amylose while forming the blue complex and partly remains free. The equilibrium normality of the free and the bound iodine at half-saturation of amylose by iodine is designated as [If]v and [Ib]w, respectively. The stability of the poly iodine chain formed within the axis of amylose helices depends on its length, i.e., indirectly on the DP of the amylose helices: the greater this stability, the lower the [If]v value. The amylose molecule consists of helical segments. Such a molecule may behave as a random coil. The average length of the helical segments in freshly prepared amylose-iodine complexes depends on temperature, pH, iodide concentration, the presence of other complex-forming agents, and the DP of the amylose. This latter factor is investigated in the present paper. By the aid of an automatically recording photometrictitrating device the coherent values of [Ib] and [If] were determined. Plotting these values against DPn for mechanochemically degraded as well as for periodateo-xidized amyloses resulted in curves consisting of two linear sections. The break of the curves occurred between DPn 110 and 130. It was concluded that below DPn = 100 the DP of helical segments (= sDPn) is identical to the DPn of the total molecule, i.e., the molecule consists of only a single, relatively stiff helix. Above this limit the molecule contains several helical segments. The DP of these helical segments can be calculated as follows: sDPn = 141.1 - 10.2 × 105[If]v. This equation is considered to be valid for 0.5-0.6 mg. amylose in 100 ml. 0.1N HCl at 20°C., λ = 650 mμ, euuvet diameter 3.4 cm., the feed rate of the iodate-iodide titrating solution (in acid medium resulting in a 5 × 10-3N I2 solution with a molar iodide to iodine ratio of 1.5) is 0.4ml./min. Amylose molecules of, e.g., DPn = 1380 consist of an average of 11.4 segments having a DP of about 120 and consisting of an average of 15-18 helical turns.

Notes: The electrochemical possibilities for investigation of nucleic acids with high molecular weight are restricted to the determination of the adsorption behavior. According to our experience the alternating current polarography (Breyer-polarography) is mainly appropriate for the characterization of changes in the secondary structure of DNA. The Breyer-polarogram shows the alternating current of the dropping electrode in dependence on their potential which varied from 0-2 v. negative against the normal calomel electrode (NCE). By addition of native DNA to the supporting electrolyte (buffer solution) the current drops down in the range of adsorption between 0 and 1 v. At 1.16 v. against NCE the desorption takes place together with the formation of a rounded desorption peak. The investigation was carried out in phosphate buffer solution 0.1m with 0.075m NaCl or in a phosphate buffer 0.18m with 0.03m NaCl. In the pH range above pH 8 NaOH was added to realize the higher pH values. A calf thymus DNA sample having a mean molecular weight of about 18 million was used. The concentration of DNA was 5 × 10-3-1 × 10-1 wt.-%. The polarographic measurements were performed with an a.c./d.c.-polarograph “GWP 564” from Akademiewerkstätten für Forschungsbedarf der Deutschen Akademie der Wissenschaften zu Berlin (DAW). The denaturation of the double helix causes a sharp desorption peak at negative potentials of the alternating current polarogram. This new criterion for the helix-coil transition is due to formation of unpaired bases. These nearly free bases undergo a specific adsorption and the desorption takes place within a narrow potential range. Nevertheless, at present time an electron transfer to particular bases cannot be excluded at special conditions. The increase of the sharp peak permits to estimate: (a) the melting curve of the double helix in agreement with spectroscopic measurements; (b) the photolysis of the double helix; (c) the strand separation in acid and alkaline solution. In the alkaline range the sharp peak increases and reaches its maximum at pH 〉 12. In the acid range, however, no sharp peak is observed and the rounded desorption peak decreases. Therefore, the best way of following the conformation changes is to measure the current difference between the curves of the solutions with and without DNA at electrocapillary-zero-potential. On the classical d.c.-polarogram one can measure small current steps only, which may be caused mainly by capacity changes. Moreover, the scission of the molecule by ultrasonic action can be followed. In this case the rounded peak of DNA increases but the sharp peak does not appear. Similar alternating current polarograms are obtained with poly-A in the native state, because helical and unordered regions coexist in the same molecule. The very rapid indication of these structure changes allows one to carry out kinetic measurements at a fixed potential with this method.

Notes: The theory of Kirkwood for the translational frictional coefficients of structures composed of subunits has been generalized in two ways in order to consider aggregates of nonidentical subunits. One of these generalizations fails when the sizes of subunits are too disparate; the other, derived from a surface shell distribution of frictional elements, is effective over the whole range of relative sizes. It is shown that, in the limit of a continuous surface distribution, a shell model reproduces Stoke's law for a sphere. Comparison is made between the frictional coefficients of spheres, ellipsoids, and rods modeled by finite numbers of subunits and by continuous shells of frictional elements, and those calculated from other theories. Agreement is generally good, though the shell model for prolate ellipsoids of revolution deviates by a few per cent from the Perrin value.

Notes: The method of matrix rank analysis has been applied to a large body of experimental data to determine and identify the minimum number of independent spectral components that, were contained within it. The optical rotatory dispersion of TMV RNA was measured in the wavelength region 230-350 mμ, for a wide range of temperatures and ionic strengths. Over the whole range of conditions considered, the observed optical rotatory dispersion spectra were found to be a superposition of two basic spectra only. Evidence is put forward relating these spectra to the single-strand and double-strand helical forms of the molecule. A model is proposed to explain the observed spectral changes in terms of an equilibrium between these two conformations, which leads to a direct calculation of the percentage composition of the double strand at any of the conditions considered. This equilibrium, while simple in general description, appears multi-state and complex in detail. This method of analysis is both powerful and of wide applicability, since it is independent of the source of the data.

Notes: An infinite series solution to the Mason-Weaver equation is presented for the case in which a synthetic boundary is formed originally between solution and solvent. Digital computations based on this series, and confirmed independently, have been made for a range of parameters. For given conditions, the maximum rate of change of concentration at the meniscus and the time at which it occurs can be easily estimated by means of the curves presented. In equilibrium experiments which commence with formation of a sharp boundary, this enables the fringes to be identified with certainty.

Notes: The course of the reversible helix formation of poly(γ-benzyl L-glutamate) (PBG) dissolved in a mixture of dichloroacetic acid (DCA) and 1,2-dichloroethane (EDC) was followed by measuring the heat capacity and the optical rotation of the system through the transition region. The results of these measurements indicate that the transition enthalpy ΔH the transition temperature Tc, and the Zimm-Bragg parameter σ depend considerably on the PBG concentration as well as on the composition of the solvent. For the standard state of infinite dilution, however, a linear extrapolation of the measured ΔH if values results in a standard value ΔH° = 950 cal./mole, independent of the solvent composition. The results of the calorimetric measurements are discussed in relationship to changes in optical rotation. Some peculiarities in the measured thermodynamic and optical properties in solutions with relatively high content of dichloroacetic acid are reported.

Notes: Helical conformations of infinite polymer chains may be described by the helical parameters, d and θ (the translation along the helix axis and the angle of rotation about the axis per repeat unit), pi (the distance of the ith atom from the axis), dij, and dij (the translation along the axis and the angle of rotation, respectively, on passing from the ith atom to the jth). A general method has been worked out for calculating all those helical parameters from the bond lengths, bond angles, and internal-rotation angles. The positions of the main chain and side chain atoms with respect to the axis may also be calculated. All the equations are applicable to any helical polymer chain and are readily programmed for electronic computers. A method is also presented for calculating the partial derivatives of helical parameters with respect to molecular parameters.

Notes: A dilatometric technique is employed to measure the volume changes occurring on denaturation of collagen solutions and tendons. Partial specific volumes of tropocollagen are calculated to be 0.686 ml./g. in water and 0.689 ml/g in 0.1M citrate buffer. From data on non-aqueous solutions, it is estimated that most of the volume change arises from changes in polymer configuration rather than from changes in solvation.

Notes: We have generated solutions to the Lamm equation to examine the effects of concentration dependence on velocity experiments. Two forms of c dependence are considered: s/s0 = 1 - kc and s/s0 = (1 + kc)-1. Features of these solutions are discussed. The magnitude of the errors resulting from the usual procedure of measuring the rate of movement of schlieren maxima or of the position at which the concentration is one half the plateau value have been examined. These errors are usually negligible after sufficient centrifugation time. The errors in using the half-plateau concentration are less than those using the movement of the peak. We have also examined a technique due to Fujita for determining D from boundary spreading when s/s0 = (1+kc)-1. This method is satisfactory when s/s0 is actually of this form, or under certain limitations when s/s0 = (1 + kc)-1. Creeth has shown that under certain conditions the concentration gradient, curve remains virtually unchanged in shape after separating from the meniscus. When this occurs it is possible to estimate s/D from the data. The condition for such a steady state is that kc0 be sufficiently large. Numerical confirmation of this method is presented in the final section.

Notes: Preliminary experiments have been carried out which measure the variation in the intensity of the light scattered by DNA solutions under the influence of an electric field. Data have been collected on the length of DNA molecules, their electric polarizability, and their dispersion behavior.

Notes: Information concerning the structures of rA-rU, rA-rU2 rI-rC, rA-rI2, and acid rA helices in solutions is reported. Through the use of diquaternary ammonium salts of the general structure, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_2 {\rm R}_3 \mathop {\rm N}\limits^ + ({\rm CH}_2 )n\mathop {\rm N}\limits^ + {\rm R}_1 {\rm R}_2 {\rm R}_3 \cdot 2{\rm Br}^ - $\end{document} (I), it is shown that (1) the distances between adjacent negatively charged oxygen atoms on the helix increases in the following order rA-rI2 〈 rI-rC 〈 rA-rU ≤ rA-rU2; (2) the density of the helices increases in the order. rA-rI2 〈 rA-rU 〈 rA-rU2 〈 rI-rC; (3) there is a large hydrophobia site in rA-rI2 and possibly also in rA-rU, rA-rU2, and rI-rC helices; (4) the results of the interactions between the salts of type I and the helices may be formulated in semi-quantitative terms by the use of two parameters, α, and β which are shown to be related to the charge separation and the density of the helices, respectively; (5) the studies in solutions compare favorably with the x-ray studies on the fibers; and (6) the acid rA helix differs significantly from the other helices by the fact that the electrostatic interstrand interactions between the negatively charged oxygen atom of a phosphate group and the positively charged 10-amino group of adenine contribute significantly to the stabilization of the helix, and thus it is found that the presence of the salts, I, leads to a significant destabilization of the acid rA helix.

Notes: The half molecules of 186 DNA have been isolated by the Hg(II)-Cs2SO4 density gradient centrifugal ion technique. The buoyant densities of the two halves in CsCI at 25°C. are 1.713 and 1.709 g./cm.3, corresponding to GC contents of 54% and 50%, respectively. Similarly, 5-bromouracil labeled λ DNA halves were separated. The isolation of the four DNA halves made it possible to test for homology in base sequences between the cohesive ends of λ and those of 186. There was no indication of any significant homology in base sequences between the cohesive ends of the two DNA's, as indicated by the absence of a band with intermediate buoyant density in CsCI when either half of 186 DNA was annealed with either half of 5-bromouracil labeled λ DNA and then centrifuged. The lack of cohesion between the two DNA's made it possible to demonstrate unequivocally the formation of interlocked rings (catenanes) between the two DNA's. The existence of a dimeric catenane is evidenced by the formation of a species of intermediate buoyant density when 5-bromouracil labeled λ DNA is cyclized in the presence of cyclic 186 DNA of a relatively high concentration. The molecular weight of one DNA relative to the other can be calculated from the position of the dimeric catenane in a density gradient by using the method of Baldwin. The result was in complete agreement with our previous measurements from the sedimentation coefficients and by electron microscopy. The probability of dimeric catenane formation when one DNA is cyclized in the presence of another DNA is discussed. The experimental results agree with the theoretical expectation.

Notes: Sterically allowed forms of the poly-N-methyl-L-alanine chain were found by calculation of conformational energies as a function of the rotation angles of its chain bonds. The lowest energy form seems to be a right-handed, approximately threefold helix.

Notes: Oriented amylose fibers in the V form were prepared and subjected to x-ray analysis. Unit cells and the probable space group of P212121 were determined for the V anhydrous and V hydrate forms of amylose; the analysis confirms previous predictions of these structures based on x-ray powder patterns. Chain folding in V amyloses is discussed in view of crystallographic evidence and folding experiments conducted with space-filling models. Reported also is evidence for amylose helices having diameters intermediate between 13.0 and 13.7 A.

Notes: Conformational energies of the poly-N-methyl-L-alanine chain have been calculated as a function of the rotational angles of its skeletal bonds, taking into account torsional potentials, van der Waals repulsions, and London attractions. Four pronounced minima in the energy were found; the relative magnitudes of the energies at these minima suggest that the preferred conformation of this chain is either a right-handed, approximately threefold helix, or a slightly distorted, left-handed α-helix. Inclusion of an estimate of the dipolar contribution to the total conformational energy does not significantly affect this conclusion.

Notes: The equilibrium normality [If] of free iodine in amylose-iodine complex formation is a function of the length of the polyiodine chains. This length depends on the DP of helical segments of amylose (sDPn). Values of [If] and of the concentration of the bound iodine [Ib] were determined by the continuous photometric titration with automatic recording. Plots of [Ib] versus [If] give an integral distribution curve. Since the relation between [If] and sDPn is known, the graphic differentiation of the [Ib] versus [lf] curve furnishes the differential distribution curve, representing the mass distribution of the helical segments according to their DP. The peak of this curve is characteristic of the percentage and DP of those helical segments, which occur in the largest amount. On the basis of the differential distribution curve the polymolecularity of the investigated sample may be judged. The titration of amylose samples degraded by various methods gives different distribution curves. Titrating mixtures of samples with widely differing average DP values results in differential curves having more than one maximum.

Notes: The electronic absorption and circular dichroism spectra of the DNA-acridine orange complex have been measured over a range of ionic strength, pH, and DNA phosphate to dye (P/D) ratios. Three circular dichroism bands associated with the long wavelength absorption band of acridine orange are induced on complex formation with DNA. Two of the dichroism bands, due mainly to dimeric dye molecules, are favored by low ionic strength, low pH (3.2), and a low P/D ratio (∼3), while the third, deriving primarily from monomeric dye, is optimum at high ionic strength, neutral pH, and a larger P/D ratio (9). The data suggest that monomeric acridine orange binds to DNA in the form of a left-handed helical array with four dye molecules per turn, while the bound dimer has a skewed sandwich conformation which is itself dissymmetric. The stereochemical relations between the bound monomer dye and the DNA are consistent with a modified intercalation model for the DNA-acridine complex.

Notes: The degree of helicity θ of a series of homologous polypeptides as a function of solvent composition was investigated. The polypeptides studied were: poly-N5-(3-hydroxypropyl)-L-glutamine (PHPG) as well as the corresponding 2-hydroxyethyl and 4-hydoxybutyl derivatives (PHKG and PHBG, respectively). PHPG, which is nonhelical in formic acid, attains helicity on addition of relatively small amounts of formates, formamide, and urea to its solution in formic acid. This demonstrates that the high acidity of pure formic acid is largely responsible for its helix-breaking power-probably through protonation of the peptide bonds. In formic acid-water mixtures all three polymers show a maximum in degree of helicity at a mole fraction of about 0.3 formic acid. This is interpreted as being due to interaction between the two helix-breaking solvents, which results in the formation of an inactive molecular species. It is shown that solvent-induced transitions with helicity maxima are predicted by the Bixon-Lifson treatment when applied to this system.

Notes: Dielectric properties of human and horse hemoglobin were studied at frequencies ranging from 20 kc./sec. to 7 Mc./sec. The relative errors in the measurements were usually less than 10-3 even for mildly conducting solutions (10-3M KCl). The experimental setup allowed us variation and measurement of the degree of oxygenation of the protein and to determine its dielectric parameters. Our main conclusion is that it was not possible to find any variation of the dielectric increment for hemoglobin oxygenation levels of 25, 50, 75, and 100%, approximately. This result is at variance with some previous reports. We cannot give the reason for this discrepancy but discuss some possible explanations. The specific dielectric increment, Δεs/c, of human hemoglobin was shown to be significantly smaller than that of horse hemoglobin (0.28 against 0.32). This physical property is lowered with increasing ionic strength I: Δεs/c = 0.28 and 0.20 for I = 10-4 and 10-3, respectively (human protein).

Notes: An expression is derived for the melting point of a polymer when in equilibrium with a solution in which binding of low molecular weight compounds to the polymer takes place. Allowance is made for the possibility that the crystalline polymer itself is a complex. The argument is a purely thermodynamic one and is based on a consideration of the change in free energy as a result of a change in binding. Allowance is made also for non-specific polymer-solvent interactions, in which the mixture of low molecular weight solvents is treated as a single solvent. Special attention is paid to “inverted” melting transitions, i.e., cases in which the melting point increases with increasing dilution of the polymer. It is shown that as a rule this is accompanied by a corresponding, inverted effect of the solvent composition on the melting point. It is further shown that-in the absence of binding, “normal” behavior at the critical point (i.e., phase separation is induced by lowering the temperature) is always accompanied by “normal” melting behavior (i.e., a decrease in melting point when the polymer is diluted). Also, “inverted” melting always implies that phase separation at the critical point is induced by heating, but the reverse is not necessarily true.

Notes: The grand-partition-function theory of the preceding paper is used to derive expressions for the number of base pairs bonded in DNA with explicit consideration of the copolymeric nature of the DNA. The following features of the DNA molecule are taken into account: (1) the DNA's from different sources have different ratios of a-t and g-c pairs; (2) the a-t pair is weaker than the g-c pair; (3) the nearest-neighbor frequencies of the two kinds of base pairs are nonrandom; (4) the stacking energies (nearest-neighbor energies) of the various combinations of pairs may be different. An ensemble is constructed in which the features (1) through (4) are introduced by means of statistical weights on the various pairs and combinations of pairs, and an expression for the corresponding partition function is written. Expressions are derived for the number of bonded base pairs and the number of helical sequences.

Notes: A method is described for formation of hydroxamic acids by direct coupling, in aqueous medium, of hydroxylamine hydrochloride and the sodium salt of a carboxylic acid. The reaction is mediated by a water-soluble carbodiimide, 1-cyclohexyl-3-[2-morpholinyl-(4)-ethyl]-carbodiimide metho-p-toluene sulfonate. Using model compounds, the production of α-, β- and γ-acyl hydroxamic acids was studied. Hydroxamic acid derivatives of α-polyglutamic and γ-polyglutamic acids were also prepared. Dinitro-phenylhydroxamate derivatives were prepared and subjected to Lossen rearrangement, and the reaction mixtures hydrolyzed. Analysis showed that α-polyglutamic acid yielded as many molecules of α,γ-diaminobutyric acid as there had been glutamic acid residues in the form of the dinitrophenylhydroxamate, and gave rise to no ammonia and succinic semialdehyde. In contrast, γ-polyglutamic acid yielded exactly twice the molar quantity of ammonia as there had been glutamic acid residues in the form of dinitrophenylhydroxamate, and also gave rise to significant quantity of succinic semi-aldehyde but no α,γ-diaminobutyric acid. Since production of the latter is characteristic of α-glutamyl hydroxamates and production of the former is associated with γ-glutamyl hydroxamates, the results indicated that the side-chain carboxyl groups of either polymer retained their identities during formation of the hydroxamic acid derivative, and no interchange had occurred between α- and γ-carboxyl groups. These methods were then used to establish that gelatin of ichthyocol contains (per 1000 total residues) at least 20 residues of glutamic acid in γ-peptide linkage. Due to the incomplete dinitrophenylation of the hydroxamic acid derivative of the protein, gelatin of calf skin collagen gave a lower figure of 10 such linkages per 1000 total amino acid residues-a value which must be considered a minimum value. These results show that γ-glutamyl peptide bonds exist in collagen.

Notes: A statistical thermodynamic treatment of thermally induced helix-coil transitions is formulated with the matrix method for an (ensemble) of system(s) in which one strand of a double helix consists of a homopolymeric polynucleotide and the other strand comprises a number of complementary oligonucleotides. Each oligonucleotide is considered to be completely bound to the longer chain when in the helical configuration and completely free from it when in the randomly coiled configuration. The case of partial binding; i.e., “dangling,” is treated in a later paper. Taken into account in both cases are intrachain “stacking” interactions between nearest neighbor residues and interchain hydrogen bonding.An approximate treatment of the characteristic equation of the formulation indicates that the reciprocal of the transition temperature (1/T0) is a linear function of the reciprocal of the degree of polymerization (D.P.) of the oligonucleotides. In the same approximation, 1/T0 is also a linear function of the negative logarithm of the absolute activity of the oligonucleotides. Transition curves obtained by exact calculation on a computer are presented for various degrees of polymerization of both the oligo- and polynucleotides. These curves show a sharpening of the transition with increasing D.P. of the long chain and the aforementioned reciprocal D.P. dependence of 1/T0.

Notes: The dielectric dispersion of polyglutamic acid (PGA) was studied in the pH range of 4-9.8. Three different dispersion curves were obtained. Above pH 6.0, where PGA has a random coil configuration, the dielectric dispersion is characterized by a large dielectric increment (ca. 450) and a relaxation time of 10-12.7 × 10-6 sec. Between pH 6.0 and 5.0, where PGA is in a transitional state with small viscosity, a dispersion curve with very small dielectric increment and also small relaxation time was observed. Below pH 5.0, where PGA has a helical configuration, the dispersion is characterized by a relaxation time of 10-12 × 10-6 sec. and a dielectric increment of about 120. The dipole moment of coil and helical forms of PGA were calculated by using Allgen's equation, and qualitative discussions of these dielectric properties are presented.

Notes: Ultaviolet absorption spectra down to 185 mμ are presented for a number of nucleic acids and synthetic polynucleotides in the helical and random forms, and of their constituent mononucleotides, as well as the corresponding nucleosides and free bases. A short wavelength absorption band is in all cases observed with a maximum varying between about 187 and 201 mμ. These bands are more intense than those near 260 mμ. The helical polymers show a hypochromic effect in this region of a somewhat similar magnitude to that in the 260 mμ region. Other spectral phenomena accompanying denaturation and degradation are described.

Notes: The inactivation of sRNA by reaction with formaldehyde has been reported as it occurs under various conditions giving differing amounts of secondary structure. The theory of inactivation of an active macromolecule by a chemical reaction is developed. Results obtained with a partially melted out secondary structure show that formaldehyde inactivates sRNA by a single reaction at any one of about ten sites, while reaction at other sites does not affect the activity of the sRNA. In the presence of Mg++ at neutral pH, a large proportion of the active molecules are completely protected against inactivation. From the correlation between the amount of secondary structure and the difficulty of inactivation, it is shown that at least a portion of the secondary structure of sRNA is essential to its amino acid acceptor ability. A comparison of results of various workers shows that formaldehyde does not alter RNA as drastically as other reagents and thus enables more discrimination between sites of reaction which are essential and those which are not essential to biochemical activity.

Notes: Infrared absorption and x-ray diffraction measurements have been made of D,L-copoly-γ-benzylglutamate fibers (cast from dioxane solutions) with various D/L ratios and with various degrees of polymerization. It was found that each chain of these copolymers consists of a random coil portion and an α-helix portion and that the conformation of the latter is similar to the α-helix of pure poly-γ-benzyl-L-glutamate. It was also found that the fraction of the α-helix portion increases with the degree of polymerization of the copolymer. A simplified polymerization mechanism has been proposed for mixtures of D- and L-amino acid N-carboxyanhydrides. A model of the molecular conformation of the D,L-copolypeptide chains derived from this proposed polymerization mechanism is in good agreement with infrared, x-ray, and other measurements. Based on the results of these observations, we discuss the number of L- or D-residues linked in succession that is required for initiating the formation of an α-helix during the course of polymerization.

Notes: Poly-L-proline I and II, polyphydroxy-L-proline II, polysarcosine, and collagen, as well as two model amides have been examined by far ultraviolet spectrophotometry. Absorption spectral data are presented. Neither in solution nor in oriented films of poly-L-proline I and II is there any indication of excition resonance splitting of the peptide absorption band. In collagen there is some, in the poly-L-prolines only minimal, hypochromicity. These observations, at least in poly-L-proline II, run counter to theory. Optical rotatory dispersion measurements in the ultraviolet indicate simple dispersion in collagen and poly-L-proline II down to at least 232 mμ. The Cotton effect (trough at 233 mμ) observed in α-helical polypeptides and proteins is absent. The implications of these findings are discussed.

Notes: The helix - coil transition of poly-L-glutamic acid (PGA) in aqueous solutions was followed by volume changes, ΔV, and also differential refractive indices, Δn. The increase in ΔV or decrease in Δn upon mixing the sodium salt of PGA with dilute HCl gave three straight lines between pH 7 and 4, the two breaks corresponding to the transition zone observed by other physical methods. For the reaction: —COO- + H+ → —CO-OH, ΔV per mole of H+ bound was 11.4 and 11.1 ml. in 0.01 and 0.2M NaCl solutions, respectively. An additional conformational change of about 0.5-1 ml. per amino acid residue was observed for the reaction: coil → helix, after taking electrostatic interaction into consideration. This was probably due to the release of the water of hydration at the amide linkages when the polypeptide coil is converted into the α-helix, or even the occurrence of voids in the polypeptide chain as a result of imperfect packing of the atoms, although the origin of this volume change is still not fully understood at the present time. The volume changes as calculated from Δn by assuming a constant polarizability of the polymer was found to be higher for the association reaction than those mentioned above. On the other hand, the calculated ΔV for the transition was in fair agreement with those by direct measurements.

Notes: Dye-macromolecule complexes provide good models for the study of the effects of coupling between chromophores. In addition to modifications of the visible and UV absorption spectra of the dyes at small interchromophore distances, very efficient energy transfer has been demonstrated at longer distances. The probability of nonradiative transition increases with the number of excitation transfers so that an array of oscillators close to one another becomes nonfluorescent. The insertion of a dye molecule, acting as a trap for the excitation energy, in the highly ordered system of chromophores constituted by the purine and pyrimidine bases of native DNA has given results supporting the intercalation model of Lerman and providing an experimental approach to the problem of the path length of energy migration in the DNA molecule. The average excitation path length seems to be of the order of only ten base pairs, a result which can explain the lack of fluorescence of the DNA.

Notes: The sedimentation, diffusion, and osmotic behavior of poly-L-lysine hydrochloride is examined over a wide range of ionic strengths and in solutions which range in relative composition from a swamping excess of added salt (suppression of charge effect) to salt-free solutions (maximum effect). The charge effect is found to essentially obey the theoretical treatment proposed in Part I of this work. The frictional coefficient of the macroion in salt-free solutions is comparable to that of the fully stretched chain. In excess of salt the friction is appreciably smaller, its magnitude not varying greatly with ionic strength. The molecular weight is determined osmotically and also from diffusion-sedimentation, with the charge effect suppressed by addition of salt or eliminated through the use of non-ionized forms of the polymer; a reasonable agreement is obtained between the methods. The influence of small ions on sedimentation is also examined. The secondary salt effect is found to be much smaller than that predicted theoretically; on the other hand, the substitution of different counterions in the absence of secondary salt effect gives rise to changes of the expected magnitude.

Notes: Poly-β-hydroxybutyric acid has been isolated from two bacterial sources by two different procedures. Molecular weight and intrinsic viscosity for the two samples were vastly different. This was blamed on degradation occurring during polymer isolation. An optical rotatory dispersion curve for the high molecular weight sample showed a sharp increase in specific rotation at wavelengths less than 450mμ. From this fact and the reported optical activity of the monomer it is concluded that the polymer is stereo-regular. X-ray examination of the “native” and “regenerated” polymer yielded the same crystalline pattern. Electron diffraction and x-ray data on single crystals of the polymer indicate a fiber repeat of 5.9 A. The value can only be reconciled with some kind of helical conformation in the solid state.

Notes: It has been suggested previously that water is a nearly indifferent solvent for amylose on the basis that the exponent a of the Mark-Houwink equation is very nearly 0.50 and the second virial coefficient A2 is extremely small. It is shown that such solutions do not show the expected precipitation on cooling and the temperature coefficient of the intrinsic viscosity is small and negative. It is suggested that water is both an indifferent and a nearly athermal solvent for this polymer. Various lines of evidence suggest the polymer to exist as a very stiff coil in this and in other solvents. Variations in the intrinsic viscosity and radius of gyration in various solvents show the importance of skeletal effects in addition to the usual osmotic effects. Application of the Porod-Kratky wormlike coil model leads to unreasonably short persistence lengths if the contour length is based on a fully extended conformation but large and reasonable values of the order 40-70 A. if it is assumed that the basic conformation is the helical one observed in various amylose complexes in the crystalline state. As was previously known, the specific optical rotation decreases sharply in aqueous solutions above approximately pH 12. Accompanying this change in rotation there is first a decrease, then an increase in intrinsic viscosity. This later behavior is strikingly reminiscent of the known behavior of polyglutamic acid in the pH-dependent transition from helix to coil. It is concluded that the conformation is that of a stiff coil with essentially helical backbone contour in neutral solution, and the decrease in rotation and in intrinsic viscosity at high pH results from a partial breakdown of the helical structure with a concomitant increase in backbone flexibility. The increase in viscosity and radius of gyration in extreme alkaline solution is probably due to a polyelectrolyte expansion of the polymer coil. Some other miscellaneous observations which are in accord with this model are also pointed out.

Notes: The Lifson-Roig theory for the helix-random coil transition in polyglycine has been modified to take side-chain interactions into account. The modified theory is developed specifically for poly-L-alanine which probably contains a β1-α4 hydrophobic bond. A conditional probability, expressing the strength of such a hydrophobic bond, is evaluated from the Nemethy-Scheraga data for the free energy of formation of the bond. This, together with the conditional probabilities for the states of the backbone chain, permit an evaluation of the partition function and properties of the helix-random coil transition. It is seen that the hydrophobic bond renders the poly-L-alanine helix much more stable than the corresponding polyglycine one, in agreement with data obtained by Gratzer and Doty.

Notes: Optical, hydrodynamic, and titration properties of polyribouridylic acid (poly U) were investigated in 0.2M Na+, pH 6. Above 15°C., poly U was shown to be a randomly coiled single chain, devoid of secondary structure. There is no shear rate dependence of viscosity; molecular weight is independent of ionic strength; there is virtually no conformationally dependent hypochromicity; no anomalous optical rotatory dispersion; and no anomalous titration behavior. The dependence of the sedimentation constant and intrinsic viscosity on molecular weight was determined. Poly U was shown to be the most highly expanded of all synthetic and naturally occurring randomly coiled polynucleotides.

Notes: Free poly-L-lysine base has been synthesized from ∊,N-trifluoroacetyl-α,N-carboxy-L-lysine anhydride via poly-∊,N-trifluoroacetyl-L-lysine (IV). No racemization occurred during the removal of trifluoroacetyl groups from IV with 1M piperidine. Measurements of optical rotatory dispersion suggest that IV exists in methanol in a helical form. The synthesis of poly-L-lysyl rabbit serum albumin is also described.

Notes: The helix-coil transition temperature Tc of poly(γ-benzyl L-glutamate) in binary solvent mixtures of dichloroacetic acid and 1,4-dichlorobutane, 1-chlorooctane, or 1-chlorododecane have been measured. A treatment is presented with which the transition enthalpy can be calculated from the observed dependence of Tc on solvent composition. Results are compared with previously obtained calorimetric data. The underlying assumptions of the calculation are discussed.

Notes: A marked molecular weight fractionation accompanies the demixing or phase separation resulting from the complex coacervation of mixtures of aqueous solutions of salt-free isoionic unfractionated gelatins with pI's of 5 and 9. Viscosity studies show that the fractionation is such that the concentrated phase tends to maintain constant, homogeneous composition. A second feature, seen in phase volume and concentration measurements, is a marked self-suppression of coacervation intensity with increasing mixing concentration. These data were interpreted in terms of a dilute-phase aggregate model which assumes nearly equal electrostatic free energies of mixing in dilute aggregate and concentrated random phase. The driving force for phase separation is the entropy increase upon formation of the random phase but demixing also depends upon the polymer-solvent interaction parameter χ, in the same fashion as in simple coacervation. The dilute-phase aggregate model indicates that the sharp molecular weight selection takes place in the aggregate formation step and explains the self-suppression. Phase equilibria studies utilizing fractionated, paucidisperse high molecular weight gelatins, emphasize the requirement for concentrated phase homogeneity and indicate that aggregates of different molecular weight may act as different components, so that χP1Q1,PkQk 〉 0, bringing about a separation of the system into three or more coexisting phases. The formation of several coexisting phases from a homologous polyelectrolyte system and the very marked requirement for phase homogeneity suggest that the phenomenon of complex coacervation is a very good model for some of the essential steps in the pre-biologic organization of polymeric polyions.

Notes: Light scattering of multichain poly-α-amino acids was studied in dimethylformamide (DMF). The polymers consisted of a backbone of poly-L-lysine of degree of polymerization n with side chains of benzyl L-glutamate and benzyl L-aspartate of degree of polymerization, m, on each ε-amino group. The backbone length n is known and m is obtained by amino acid analysis. The results on a series of such materials confirm this structure and show that the molecules are dissolved in highly compacted conformations. It was found that DMF is a poor solvent for these polymers. In the case of the higher molecular weight polymers, the solutions initially were not molecularly disperse. The aggregates were resistant to dilution in the experimental range. Mild heat treatment, however, disaggregated the solutions irreversibly, and the light-scattering data indicated that a structural rearrangement of the molecules had occurred.

Notes: The intrinsic viscosity, sedimentation and diffusion of a series of branched, multichain poly-α-amino acids having a poly(L-lysine) backbone and poly(γ-benzyl L-glutamate) and poly (β-benzyl L-aspartate) side chains was studied at room temperature in dimethylformamide. The molecules were found to be extremely compact structures in which the molecular backbone is either lying along the major axis in a slightly twisted configuration (the longer the side chain the smaller the twist) or is coiled up in the form of a disk with backbone and side chains coplanar. Heat treatment (to 70°C.) introduces only small changes in the hydrodynamic parameters showing that the heat-labile aggregates detected by light scattering are reversibly broken up during the hydrodynamic measurements. The above structural information concerns the initial metastable conformation of the molecules which is irreversibly destroyed by heat treatment.

Notes: The optical rotatory dispersion and ultraviolet absorption spectra of the 64 trinucleoside diphosphates containing the bases A, U, C, and G have been calculated by using a simple semiempirical approach. These calculations accurately predict the optical properties of the nine trimers for which extensive experimental results are available. The computed optical data should be useful in the identification of oligonucleotides obtained in the course of sequence determination of ribonucleic acids and should simplify the determination of the concentration of oligonucleotides in aqueous solution. Additional calculations indicate that it should be possible to analyze most, mixtures of sequence isomers of trinucleoside diphosphates by direct, measurement of the ORD of the mixture at neutral pH.

Notes: The equilibrium binding constants of Cd++ and Cu++ to native and denatured calf thymus DNA were determined polarographically. The binding constants are an exponential function of the potential at the binding site and as such they vary with ionic strength and with the charge on the DNA molecule. The correlation between the fraction of sites occupied by heavy metal ions and between the thermal stability of DNA in solution is discussed.

Notes: Complex shear viscosity η* = η′ - iη″ of poly (L-glutarmic acid) solution was measured by the torsional crystal method at 50 kc./sec. as a function of pH. A sharp peak was found at the midpoint of the helix-coil transition region in both η′ and η″. The relaxation time is calculated from η′ and η″ assuming a single relaxation process and the peak value at the midpoint of transition is estimated at 10-6 sec. Such behavior agrees well with the prediction from the theory of Schwarz. The attenuation of longitudinal sound waves at,3 Me./sec. was measured as a function of pH for solutions of poly(glutamic acid), glutamic acid, and gelatin. A small attenuation peak was observed for the three solutions, the peak height being almost, the same for them. The peak is interpreted in terms of the dissociation reaction of side chains.

Notes: We report the circular dichroism (CD) spectrum of poly-Lacetoxyproline in trifluoroethanol, a solvent in which the form I to form II conformational isomerization occurs slowly enough to permit observation of the spectral changes. A comparison is made to poly-Lproline. As judged by the similarity of the CD spectra, the conformations of the corresponding forms of the two polymers must be nearly the same. Transition assignments are proposed; these are shown to agree with the theoretical calculations of Pysh. There is a serious unexplained discrepancy between our solution data and those of Fasman for poly-Lacetoxyproline.

Notes: The dielectric relaxation of DNA solutions has been investigated with and without extraneous ions covering a wide frequency range. The effect of monovalent ions such as Na, K, and Li as well as divalent ions such as Mg, Ca, and Hg have been included in the study. These ions are found to have a profound effect on the dielectric increment and the relaxation time without affecting the molecular dimension drastically. This dielectric effect is interpreted as indicating the importance of counterion fluctuation on the low frequency dielectric constant of DNA in solution. The effect of an organic ion, tetra-methylammoniun bromide, has also been studied. This ion has no noticeable effect. A simple theory is derived on the basis of a microscopic model to account for the effect of external ions on the dielectric behavior of solutions of DNA.

Notes: Block and random copolymers of γ-benzyl L-glutamate and glycine were studied by optical rotatory dispersion methods in order to ascertain the extent and stability of the α-helix formed by these polymers in appropriate solvent mixtures. Results indicate that when in solution such polymers do contain sections of α-helix. However, it appears that glycine does not readily fit into the α-helix which is largely due to the γ-benzyl L-glutamate segments. Further, there are indications that the helical sections in the random copolymers are due to the nonrandomness of the polymerization.

Notes: It is demonstrated that, poly(A + U) and poly(I + C) are both formed under low ionic strength conditions. Continuous variation studies indicate the formation of copper(II) complexes of poly A, poly C, and poly I, but not of poly U. Copper(II) in a 1:1 ratio to polynucleotide prevents the formation of poly(A + U) and brings about the dissociation of the poly (A + U) complex produced in the absence of the metal. Poly (I + C) is similarly dissociated by copper(II) ions. The addition of sufficient electrolyte reverses the copper(II) induced dissociation of poly(I + C). The effect of copper(II) on ordered synthetic polynucleotides is thus very similar to its effect on DNA.

Notes: The synthesis and some of the physical-chemical properties of tricopolymers of L-glutamic acid, L-lysine, and L-alanine are reported here. The molar ratios of the glutamyl: lysyl: alanyl residues were 1:1:X or 3:2:X, where the alanyl content X was increased in regular steps. The α-helix content calculated from the optical rotatory dispersion of the polypeptides is compared with a predicted helix content estimated from the composition of the polymers and the known behavior of the homopolypeptides at pH 3, 8, and 12. At pH 3 copolypeptides containing 20 mole-% or more alanine exhibit a helix content equal to the sum of their alanyl and glutamyl residue contents. At pH 8 the helix content equals the alanyl content when the latter was 40 mole-% or higher; at lower alanyl contents the electrostatic interaction between charged glutamyl and lysyl residues makes some contribution. At pH 12 the amount of helix observed is proportional to the mole ratio of alanine residues present in the polymer. The helix content of a tricopolymer containing 1:1:3 mole ratios of glutamyl: lysyl: alanyl residues was determined in solutions of lithium bromide and in urea solutions. Both reagents led to a decrease in helix content at pH 3 and 8 to a minimum of approximately 20% helix in 8M urea or 5.5M LiBr. The helix-random chain transition curves at pH 3 and 8 are parallel when the urea concentration is varied, but differ in shape when the lithium bromide concentration is varied at pH 3 and 8. The mode of action of these two “denaturing” reagents may thus be different. Heating the same tricopolypeptide at pH 3 or 8 from 5 to 80°C. also led to a helix-random chain transition centered at approximately 45°C.

Notes: Potentiometric titration curves of the silver(I) complexes of cytidine, adenosine, and uridine show little uptake of base below pH 7, unlike the curve for silver(I)-guanosine, which shows extensive base uptake at neutral pH. This observation is correlated with spectrophotometric data showing little difference between the silver complex spectra of adenosine, cytidine, and uridine and the spectra of uncomplexed nucleosides, except at high pH, but showing a great difference between the silver complex spectra of guanosine and inosine and the corresponding uncomplexed nucleosides even at pH 6. Similar comparisons of the silver complexes of poly A, poly C, poly I, and poly U, both by potentiometric titration and by spectrophotometry, show that poly I behaves like guanosine and inosine as expected, differing from poly A and poly C. However, poly U behaves like poly I and thus does not resemble uridine in its complexing behavior. There is thus a dichotomy between poly A and poly C on the one hand in silver complexing phenomena, compared with poly U and poly I on the other. When silver(I) is added to systems containing zinc(II) and various polynucleotides, the same dichotomy is noted. Silver(I) inhibits the degradation by zinc(II) of all four polynucleotides, but the degradation of poly I and poly U is prevented virtually completely. Silver(I) alone has no degradative effect on RNA and inhibits, the zinc(II) degradation of RNA. Polynucleotide complexes in which silver(I) and zinc(II) are simultaneously bound to different positions on the macromolecules are postulated as intermediates in the inhibited degradation reactions.

Notes: Die basenkatalysierte Kondensation von Benzil mit Guanidin oder n-Butyl-guanidin führt nebeneinander zu 55-Diphenyl-glykocyamidin (Ic) und 7.8-Diphenyl-glykoluril-2.5-diimid (IIc) bzw. 3-(IIIc), sowie N2-[n-Butyl]-5.5-diphenyl-glykocyamidin (IVc) und 7.8-Diphenyl-glykoluril-2.5-bis-n-butylimid (Vb). Wie schon bei der früher untersuchten Kondensation mit Benzylguanidin, begünstigt Temperaturerhöhung die Bildung der Glykocyamidine, Temperaturerniedrigung die der Glykoluril-diimide, Erhöhung des pH im Medium die Bildung der N2-substituierten Glykocyamidine (bzw. mit Guanidin die des N-unsubstituierten Glykocyamidins), Erniedringung des pH die der 3-substituierten Glykocyamidine und Glykoluril-diimide.

Notes: Nach der Reissert'schen Methode wurden 4-, 5-, 6- und 7-Methoxy-oxindol synthetisiert und im UV-Spektrum verglichen. Drei dieser Oxindole wurden mit Propionaldehyd zu den 3-Propylidenverbindungen kondensiert, die durch katalytische Hydrierung in die 3-Propylderivate verwandelt wurden. Die Anlagerung von Butylmercaptan oder Thiophenol an die exocyclische Doppelbindung führt zu 31-Thioäthern. Das 4- und 6-Methoxy-oxindol wurde nach SUGASAWA u. a. zum entsprechenden Indolin reduziert. N-Acetyl-6-methoxy-indolin zeigt ein den Amanitinen sehr ähnliches UV-Spektrum.

Notes: Aus NaPHC6H5 und 1.2-Dichlor-äthan entsteht Äthylen- 1.2-bis-monophenyl-phosphin (I). Es wird durch Phenyllithium zu C6H5(Li)P -CH2·CH2-P(Li)C6H5 (V) metalliert, das mit ClCH2.CH2Cl bzw. CH3J das 1.4-Diphenyl- 1.4-diphospha-cyclohexan (VI) bzw. Äthylen- 1.2-bis-methyl-phenylphosphin (III) bildet. III ist auch aus Äthylen- 1.2-bis-[hydrogen-methyl- phenylphosphoniumjodid] und Natriummethylat zugänglich. VI gibt mit Schwefel ein Bis-P-Sulfid, das in einer cis- und trans-Form existiert.

Notes: Die Äthylester von Fluoro-mono- und -diphosphorsäuren erweisen sich als starke Alkylierungsmittel. So werden Carbonsäuren in ihre Äthylester, Chlor- und Jodwasserstoff in die Äthylhalogenide übergeführt. Nach Entfernen der Alkylierungsprodukte können die den eingesetzten Estern zugrunde liegenden Fluorophosphorsäuren papierchromatographisch und durch Derivate in den Reaktionsrückständen nachgewiesen werden, besonders die noch nicht beschriebene symm. Difluoro-diphosphorsäuren. - Weiterhin werden geeignete organische und anorganische Salze durch Fluorophosphorsäureester alkyliert, wobei neben den Alkylierungsprodukten die entsprechenden Salze der eingesetzten Fluoro-phosphorsäure, u. a. die ebenfalls noch nicht beschriebenen symm. Difluoro-diphosphate, in z. T. guten Ausbeuten und großer Reinheit entstehen. - Das Difluoro-diphosphation P2O5F22⊖ ist in neutraler wäßriger Lösung relativ stabil.

Notes: Strukturen und Bildungsweisen der über 1-Halogen-2-Metall-cyclcohexen entstehenden Kohlenwasserstoffe C18H24 und C24H34 werden diskutiert. Herkunft und Konstitution zeigen auf, daß sich intermediär auftretendes Cyclohexin zum Octahydrobiphenylen III dimerisiert, das in Diels-Alder-Reaktionen Cyclohexin zu V und II zu IV addiert.

Notes: Durch eine röntgenographische Strukturuntersuchung wird bewiesen, daß dem Samandaridin, einem Nebenalkaloid aus dem Gift des Feuer-und Alpensalamanders, die Konstitution und Konfiguration IIa zukommt.

Notes: Die Methanolyse des 5-Hydroxy-3-acetoxy-B-norcholestan-säure-(6)-lactons (VII) führt in normaler Reaktion zu X und nicht zu einem Umlagerungsprodukt, entsprechend III (OH statt OAc), wie von DAUBEN und Mitarbb.1,2) angegeben. Ähnlich liefert Hydrolyse bzw. Äthanolyse die entsprechenden B-Norcholestan- Derivate VIII bzw. VI.

Notes: Raman- und IR-Spektren primärer und sekundärer Propyl-und Butyl-natrium-thiosulfate werden aufgenommen und ihre Frequenzen zugeordnet. Die unterschiedliche chemische Stabilität dieser Stoffe steht in keinem direkten Zusammenhang mit ihren Schwingungsspektren.

Notes: 12-Dibrom-cyclohexen sowie 1-Fluor-2-brom-cyclohexen und 1-Fluor-cyclohexen, deren Synthesen beschrieben werden, führte man auf metallorganischer Basis in 2-metalliertes 1-Halogen-cyclohexen über, das sich als zu kurzlebiges Gebilde in allen Fällen dem Nachweis entzog. Das sofort entstehende Cyclohexin erwies sich als sehr additionsbereit, wie die Folgeprodukte bei Einwirkung von Butyllithium einerseits und von Diphenyl-isobenzofuran andererseits aufzeigten. Der Chemismus der Abwandlung des Diels-Alder-Adduktes VII zu VIII und IX unter den herrschenden Versuchsbedingungen wird geklärt.

Notes: Aus 2-Isothioureido-tetronsäure (V) entsteht durch alkalische Hydrolyse 2-Mercapto-tetronsäure (VI), die sich unter intermolekularer Schwefelwasserstoff-abspaltung leicht zu 22′-Bis-tetronsäure-sulfid (VII) umsetzt. Aus den Alkalisalzen der 2-Mercapto-tetronsäure (VI) lassen sich stabile Acyl- und Alkyl-derivate darstellen. Die Oxydation von VI führt zum 22′-Bis-tetronsäure-disulfid (IXa). Die IR-Spektren stabiler 2-Mercapto-tetraonsäure-Derivate deuten -übereinstimmend mit dem chemischen Verhalten  -  auf die Enolform dieser Verbindungen hin.

Notes: Eine brauchbare Synthese der 1.3.6.2′.3′.4′.6′-Heptaacetyl-α-D-cellobiose mit freiem 2-OH wird beschrieben. Die Struktur wird durch Mesylierung gesichert.

Notes: Die Synthese von 2-Chlor-bzw. 2-Brom-2-desoxy-D-arabinose und -ribose aus Diacetyl-D-arabinal über die Halogenadditionsprodukte wird beschrieben. Ausgehend von diesen Verbindungen wird eine neue praktische Darstellungsweise der 2-Desoxy-D-ribose ausgearbeitet.

Notes: Halogen-acyl-aldosen ergeben bei der Reaktion mit Bis-[benzoxazolthionyl]-quecksilber in Dimethylformamid N-[Acyl-glykosyl]-benzoxazolthione, mit Benzoxazolthion-natrium in Äthanol S-[Acyl-glykosyl]-benzoxazolthione. Durch Entacylieren erhält man freie N-bzw. S-Glykosyl-benzoxazolthione. Die Struktur der Verbindungen geht aus den UV-Absorptionssspektren hervor.

Notes: Zinntetraphenyl reagiert zwischen 190° und 210° mit mehr als zwei Äquivv. Schwefel unter Bildung von Diphenylsulfid und polymeren Phenylzinnsulfiden, die umso weniger Phenylgruppen am Zinn enthalten, je mehr Schwefel eingesetzt wird. Oberhalb von 220° entsteht quantitativ Zinnsulfid.

Notes: Unter Verbesserung eines bisher nicht beachteten Verfahrens von F. SACHS, für dessen Verlauf ein Reaktionsmechanismus vorgeschlagen wird, werden 16 Amidine, darunter 7 noch nicht bekannte, dargestellt.

Notes: Die durch Benzophenon primär dehydrierend photosensibilisiterte Autoxydation von sek. Alkoholen führt durch R-H-substituierende Addition von O2 glatt zu den bisher unbekannten α-verzweigten [α-Hydroxy-alkyl]-hydroperoxyden 2). Die Reaktion wurde auf die Darstellung von Ätherhydroperoxyden ausgedehnt. - Der Bäckströmsche Reaktionsmechanismus wird unter Berücksichtigung der bisher übersehenen Reaktionen modifiziert.

Notes: 1.4.5-Trimethyl-napthalin wird durch Natrium in flüssigem Ammoniak zu einen Gemisch von 1.4.5-Trimethyl-Δ6- und -Δ7-dihydronaphthalin reduziert. Die reduzierende Methylierung, d. h. die Umsetzung seiner Natriumverbindung mit Methylbromid, läßt nur ein Methyl unter Bildung von 1.4.5.8-Tetramethyl-Δ2-dihydronaphthalin in das Molekül eintreten. 1.4.5.8-Tetramethyl-naphthalin wird auf die gleiche Weise nur zu einem Gemisch ungefähr gleicher Teile von Δ1- und Δ2- Dihydroisomerem und ebensoviel von einem leicht veränderlichen Kohlenwasserstoff, vielleicht 1.4.5.8-Tetramethyl-isotetralin, reduziert; Methyl tritt nicht in das Molekül ein.

Notes: Wie aus methylenaktiven Pyridiniumsalzen kann man auch aus vergleichbaren aliphatischen und ar-aliphatischen Nitroverbindungen Nitrone und cyanierte Anile gewinnen.

Notes: Addition von Alkyl-, und Acylsenfölen an β-Iminoketone bzw. β-Iminonitrile führte zu α-Acyl- (bzw. Cyan)-β-amino-thiocrotonamiden, die durch Dehydrierung zu 5-Amino-4-acyl(bzw. cyan)-isothiazolen cyclisiert wurden. - Aus einigen der genannten Thiocrotonamide ließen sich durch intramolekulare Kondensation auch 4-Mercapto-5-acyl-pyrimidine in guter Ausbeute darstellen.

Notes: Durch Leitfähigkeitstitrationen wird gezeigt, daß das Decavanadation, V10O286⊖, Komplexe mit Kationen bildet. Die Komplexbeständigkeit hängt dabei wesentlich vom Ionenradius des Kations ab. Es wird angenommen, daß das Decavanadation etwa kugelförmigen Bau hat und einen Hohlraum besitzt, in den ein hydratisiertes Kation unter Bildung eines Einschlußkomplexes eindringen kann. Durch die Feldwirkung des Hydratwassers an Kation acid. Dadurch wird das Decavanadation zur Bildung höherbasischer Salze befähigt.  - Für die Decavanadinsäure wird ein Strukturmodell vorgeschlagen.

Notes: Diazotiertes 2-Amino-diphenylmethan und dessen 4′-Methyl-, 4′-Methoxy- und 4′-Chlor-Abkömmlinge werden in wäßriger Schwefelsäure thermische mit und ohne Kupfer zersetzt sowie photolysiert. Die mageren Ausbeuten an Fluoren und Abkömmlingen weisen nicht auf einen starken Substituenteneinfluß bei der Cyclisierung.

Notes: β-Chinolinaldehyd wird durch Diazomethan in 3-Acetonyl-chinolin umgewandelt.  -  Bei der Einwirkung von Diazomethan auf 6-Methyl-pyridin-aldehyd-(2)] entsteht in Gegenwart von Methanol [6-Methyl-pyridyl-(2)-äthylenoxyd. In Abwesenheit von Methanol dagegen bildet sich ausschließlich 6-Methyl-;2-acetyl-pyridin. setzt man 2 Mol 6-Methyl-pyridin-aldehyd-(2) mit nur 1 Mol Diazomethan um, so entsteht 1.3-Bis-[6-methyl-pyridyl-(2)]-propanol-(3)-on-(1).

Notes: Bei der Umsetzung von Alkinolen mit Ketonen in flüssigem Ammoniak oder Dioxan werden Alkindiole, bei der oxydativen Kupplung von Alkinolen mit Kupfer(I)-chlorid und Sauerstoff werden Butadiin- bzw. Hexadiindiole erhalten, deren monovalente Reduktion zu Kumulenen führt.

Notes: 2-Methyl-dicyclopropylcarbinol (I) reagiert mit Bromwasserstoffsäure praktisch ausschließlich zum 4-Brom-1-cyclopropyl-penten-(1) (II). Mit feuchtem Silberoxid wird quantitativ der Cyclopropanring zurückgebildet. Die Methanolyse von 1-Cyclopropyl-buten-(1)-ol-(4)-p-toluolsulfonat ergab zu 93% Dicyclopropylcarbinyl-methyläther.

Notes: Aus N.N′-Thionyl-bzw. N.N′-Carbonyl-di-imidazol, Carbonsäuren und tert.-Butylhydroperoxyd wurden Percarbonsäure-tert.-butylester in 50-80% Ausbeute dargestellt. Dies ist die erste Synthese von Perestern, welche die Stufe der Carbonsäure-halogenide umgeht.

Notes: Die Darstellung der Reihe der Organoazidosilane RxSi(N3)4-x(R = CH3, C6H5; x = 3, 2, 1) gelang auf zwei Wegen: 1. Umsetzung der entsprechenden Methylchlorsilane mit Natriumazid in geschmolzenen Salzen als Lösungsmittel; 2. Umsetzung von solchermaßen dargestelltem Trimethylazidosilan mit Organochlorsilanen in Gegenwart von Aluminiumchlorid als Katalysator (Substituentenaustausch). Weiterhin konnten erstmals gemischt halogen-pseudohalogen-substituierte Organosilane, CH3SiCl2N3, CH3SiCl(N3)2 und (CH3)2SiClN3 (?) erhalten werden.

Notes: Durch die stereospezifische Reaktion der Glucose-6-phosphat-isomerase werden die zwei möglichen Fructosen-[1-T] dargestellt. Die damit unter verschiedenen Bedingungen durchgeführten Osazondarstellungen zeigen: Die Spaltung der C—H-Bindung ist reaktionsgeschwindigkeitsbestimmend, die beiden Wasserstoffe an C-1 der Fructose sind bei der Osazonbildung nicht gleichwertig. Daraus lassen sich Folgerungen für den Ablauf der Reaktion ziehen.

Notes: P(NMe2)3 reagiert mit Sauerstoff, Schwefel, Phenylazid und Schwefelkohlenstoff zu den Verbindungen (Me2N)3PO, (Me2N)3PS, (Me2N)3PNPh, Me2NP(SC(S)NMe2)2 und P(SC(S)NMe2)3. Die ME2N-Liganden von P(NMe2)3 werden mittels ÄtOH, MeCO2H und PhNH2 substituiert.

Notes: Das üblicherweise monoklin nach P21/c kristallisierende V(C6H6)2 wurde durch Umkristallisieren in organischen Medien unterhalb + 18° in einer kubischen Modifikation mit der auch bei Cr(C6H6)2 auftretenden Raumgruppe Pa3 erhalten. Kristallographische Daten des kubischen und des monoklinen V(C6H6)2 werden gegeben und denen der isomorphen Verbindungen Cr(C6H6)2 und Fe(C5H5)2 gegenübergestellt.  - Spektroskopische Untersuchungen zeigen, daß nicht nur im monoklinen, sondern im Gegensatz zu Cr(C6H6)2 auch im neuen kubischen V(C6H6)2 die D6h-Symmetrie der Benzolliganden erhalten bleibt. Angesichts der identischen Raumgruppe beider Aromatenkomplexe des Cr0 und V0 kann daher ein Gittereffekt nicht Ursache der Verformung der C6H6-Liganden im Cr(C6H6)2 zur C3v-Symmetrie sein.

Notes: Aktive Methylenverbindungen kondensieren in Gegenwart von Triäthylamin leicht mit 4-Äthoxymethylen-2-phenyl-oxazolon-(5) (I, R = C2H5O). Besitzen erstere eine zum Methylenkohlenstoff benachbarte, hinreichend nucleophile CO-Gruppe, so entstehen unter Ringisomerisierung 3-Benzoylamino-α-pyrone, z. B. XII. Fehlt eine solche, so bilden sich die entsprechenden aliphatisch substituierten Alkyliden-2-phenyl- oxazolone-(5).  -  Oxazolon-Struktur besitzen auch die Kondensationsprodukte von I (R = C2H5O) mit Enaminen des Typs IX (Formeln X und XI), und mit dem Phosphoran XV (Formel XVI).  -  4-[o-Hydroxy-aryliden]-oxazolone-(5) isomerisieren, wie Beispiel XIII zeigt, unter der Einwirkung tertiärer Basen zu 3-Acylamino-cumarinen XIV.

Notes: Aus Trimethylthionophosphat und Antimon(V)-chlorid entsteht über ein 1 : 1-Addukt quantitative Tetramethylthiophosphatacidium-hexachloroantimonat, das auch durch Methylierung des Trimethylesters mit Oxoniumsalzen erhalten werden kann. Die Eigenschaften der neuartigen Phosphonium- Verbindung sowie weitere Versuche über die Einwirkung von Alkylierungsmitteln auf tertiäre Thionophosphate werden beschrieben.

Notes: Die Untersuchung von ca. 30 Arten der Gattung Anthemis L. ergibt, daß im Hinblick auf die Inhaltsstoffe verschiedene Gruppen vorliegen In einigen Arten sind nur bereits bekannte, für den Tribus Anthemideae typische Inhaltsstoffe zu finden, während etwa die Hälfte der untersuchten Arten verschiedene Methyl-mercapto-Polyinester enthalten. Die Strukturen wurden vor allem durch ihre spektralen Daten geklärt. Die enge biogenetische Beziehung der Schwefelverbindungen zum weitverbreiteten Dehydromatricariaester wird aufgezeigt. Ein isoliertes Benzoesäureesterderivat steht offensichtlich in enger Beziehung zu den Polyinestern.

Notes: Eine neue Synthese der Homoisovanillinsäure, die vom Isovanillin ausgeht, benötigt nur 2 Stufen und ergibt eine über 80-Proz. Ausbeute. Von hier aus kommt man nach den in der Isochinolin-Chemie üblichen Methoden leicht in die Klasse der 6-Methoxy-isochinoline.