Uncharged State Research Articles

A quantitative model for partition in aqueous multiphase systems.

A model for the partition of charged molecules in aqueous multiphase systems has been developed. The partition coefficient of one component, or the overall partition coefficient of a number of components, between two arbitrary phases is expressed in terms of the difference in electrical potential between the phases (due to electrolytes present in the system), the net charges of the partitioned components and their partition coefficients in a (sometimes hypothetical) uncharged state. The fraction of material in one phase has also been described as a function of the net charges of the partitioned components. The model fits well to experimental data for partition of chromate, pyridine, ribonuclease A, two types of CO-hemoglobin and an enzyme mixture (yeast lysate) in three-phase systems consisting of poly(ethylene glycol), dextran, Ficoll and water. Minor deviations from the model are construed to be a pH-dependent uptake of ions. The data have also been used to detect differences in solvation of similar proteins, as well as the presence of several forms of some glycolytic enzymes present in yeast lysate.

Conformation of histidine model peptides. I. Conformational energy calculations for L-alanyl-L-histidine diketopiperazine.

AbstractSemiempirical conformational energy calculations were carried out for the cyclic dipeptide L‐alanyl‐L‐histidine diketopiperazine. The results indicate that electrostatic effects are probably significant in determining the conformation assumed by this molecule. When the imidazole group is in its uncharged state the most stable conformations of the molecule are those with the imidazole ring folded over the diketopiperazine ring (χ1 = 60°). Upon protonation of the imidazole group the folded conformation may be destabilized relative to conformations characterized by χ1 positions near 180°.

Sur un effet de solvant inhabituel sur une reaction de menschutkin intramoleculaire

The influence of solvation on the reaction rate of an intramolecular quaternisation, may be different from the rate observed for an intermolecular reaction of the same type. In the intermolecular reaction, if the polarity of an aprotic solvent increases, the partially charged transition state is more stable than the initial state. In the contrary, for an intramolecular reaction the conformation of the different states (initial and transition) plays an important role. So that, if the polarity of an aprotic solvent increases, one conformation of the uncharged initial state may be, by its geometry more stable than the partially charged transition state. An interpretation based on the conformation, explains why in one case and in comparison with CH 3CN, methanol accelerates the intramolecular reaction whereas the contrary is always observed for an intermolecular one.

Ionization equilibria and electronic spectroscopy of the chelating quinolinecarboxylic acids

pH and Hammett acidity dependences of the electronic absorption and fluorescence spectra of quinaldic acid. quinoline-8-carboxylic acid and their methyl esters have been studied. Conversions of the quinoline-like absorption spectra of the anions to quinolinium-like absorption spectra of the uncharged species show that the uncharged ground state species derived from the free acids consist overwhelmingly of the zwitterions. The excited singly charged cation of quinaldic acid appears to undergo an acidity-dependent phototautomerism. However, the 8-isomer does not exhibit this phenomenon. The long emission wavelengths of the esters relative to the zwitterions indicate that of the two electron-withdrawing groups, the carboxyl group is stronger than the heterocyclic nitrogen in the excited state. The fluorescence of quinoline-8-carboxylic acid in sulfuric acid could be very useful for quantitative analysis of transition metal chelates of this ligand.

Sequence peptide polymers: Part 2. Poly(leucyl-leucyl-aspartic acid)—Conformational aspects in water solution

A new sequential peptide, poly(leucyl-leucyl-aspartic acid) has been synthesized and the conformational properties in water have been examined by spectroscopic methods at different degrees of neutralization of the β-carboxyls of the aspartate residues and by potentiometric measurements. The experimental data are in agreement with the presence of α-helical segments stabilized by strong hydrophobic interactions. The calculation of the thermodynamic functions, ΔG 0, ΔH 0, ΔS 0 related to the transition uncharged random coil to uncharged α-helical state, gives at 25°C the following values: ΔG 0=−1575 cal/mol; ΔH 0=6173cal/mol; ΔS 0=26·0cal/deg mol. These values are expressed in cal/mol of repeating unit. The temperature dependence of the ellipticity and the function pH—log[ α (1−α) ] versus α, allows us to analyse the conformational stability of poly(leucyl-leucyl-aspartic acid).

One-way electron discharge subsequent to the photochemical charge separation in Photosystem I

Subsequent to the photochemical charge separation in Photosystem I, three fates are possible: (a) recombination of the photooxidized P700 + and photoreduced P430 −; (b) a cyclic electron flow involving P700 +, P430 − and another electron carrier present in its oxidized and reduced forms; and (c) a non-cyclic electron flow involving one electron donor reacting with P700 + and another electron acceptor reacting with P430 −. This note deals with a fourth fate which is brought about only when an autooxidizable secondary electron acceptor is present but the secondary electron donor is either absent or blocked. In this case, only P430 − reverts to the uncharged state in the dark by discharging its electron; P700 + remains oxidized and reverts to the uncharged state only extremely slowly.

Substitution at saturated carbon. Part XII. Calculation of the electrostatic contribution to free energies of transfer from methanol to aqueous methanol and to water of solutes and transition states. A new method for the examination of transition states

Standard free energies of transfer, from methanol to aqueous methanol and to water, of solutes and transition states have been divided into a nonelectrostatic contribution, ΔGn°, and an electrostatic contribution, ΔGe°. The value of ΔGe° for an uncharged transition state is considered to be related directly to the degree of charge separation (δ±) in the transition state. It is shown that uncharged transition states in solvolyses thought to proceed by mechanism SN1 are characterised by high values of δ±(0·8), whereas uncharged transition states in presumed SN2 solvolyses are characterised by low values of δ±(ca. 0·3); it is suggested that the values of ΔGe° and of δ± for uncharged transition states in nucleophilic solvolyses can be used as a criterion of reaction mechanism.Values of δ± for transition states in the electrophilic substitution of tetra-alkyltins by mercury(II) chloride are quite large, averaging ca. 0·55 for substitution of tetramethyltin and tetra-n-propyltin, and ca. 0·65 for the substitution of tetraethyltin. It is suggested that these values of δ± are compatible with mechanism SE2(open) for these substitutions, but not with mechanism SE2(cyclic).

A Photometric Analysis of Ultraviolet Photoreaction Kinetics of Transfer RNA

Fukutome, H., Wada, A., and Kawade, Y. A Photometric Analysis of ultraviolet Photoreaction Kinetics of Transfer RNA. Radiation Res. 37, 599-616 (1969). The kinetics of photoreactions that transfer RNA (tRNA) undergoes on ultraviolet (253.7 m,) irradiation were investigated. For this purpose, a spectrophotometric technique was developed to measure the changes in amount of uracil and cytosine residues in tRNA separately, and applied to yeast tRNA irradiated under various conditions of pH and salt composition. The photoreaction kinetics of uracil residues were found to consist of two phases with different values of apparent cross sections, which are presumed to be due to occurrence of two reactions, dimer formation and hydration. The cross sections of these reactions were shown to become larger at pH below 7, and to decrease when secondary structure develops in tRNA. The photoreaction of cytosine residues was shown to depend considerably on their state of ionization. The photoproduct produced in the uncharged state, presumably a hydrate, was shown to revert almost completely by mild heating, but the one produced in the charged state reverted

Acid–base behavior of poly (vinylpyrrolidone–vinylimidazole) copolymers

AbstractCopolymers of vinylimidazole and vinylpyrrolidone containing 0.7–24% of the former residue have been prepared. Titration behavior was examined over a range of temperature and at several ionic strengths. Intrinsic pK's, corrected for electrostatic effects, arc independent of mole fraction of imidazole residue in the copolymer. Nevertheless they are about 1.15 pK units lower than in the corresponding model small molecule, N‐ethylimidazole. Enthalpies and entropies of ionization in the copolymer are changed by ionic strength. It is apparent that the charged state of an N‐ethylimidazole residue placed in a macromolecular matrix is destabilized relative to the uncharged state because of changes in the local polymer or solvent environment.

Titration of the Histidyl and α-Amino Groups of Hemoglobin

Abstract The titration data of Antonini, Wyman, Brunori, Fonticelli, Bucci, and Rossi-Fanelli (1), for human and horse oxy- and deoxyhemoglobins, have been analyzed in a way that yields the number of groups which titrate in the pH region normally assigned to imidazole and α-amino groups. The results suggest the possibility that the group which differs between the oxy- and deoxyproteins above pH 6.5, which is the group linked to the alkaline Bohr effect, may be an α-amino group rather than an imidazole group, as has been assumed heretofore. The number of unavailable imidazole groups, which arise from histidine residues obliged to be in the uncharged state in the native protein, is about 4 per heme in human hemoglobin and about 3 per heme in horse hemoglobin. This is considerably smaller than the number of unavailable imidazoles in sperm whale myoglobin, and is also less than the number of unavailable imidazoles estimated for horse hemoglobin in previous studies.

True anomalous osmosis in multi-solute model membrane systems.

The transport of liquid across charged porous membranes separating two electrolytic solutions of different composition consists of both a normal and an anomalous osmotic component. Anomalous osmosis does not occur with electroneutral membranes. Thus, with membranes which can be charged and discharged reversibly, normal osmosis can be measured with the membrane in the electroneutral state, and normal together with anomalous osmosis with the membrane in a charged state, the difference between these two effects being the true anomalous osmosis. Data are presented on the osmotic effects across an oxyhemoglobin membrane in the uncharged state at pH 6.75 and in two charged states, positive at pH 4.0 and negative at pH 10.0, in multi-solute systems with 0.2 and 0.4 osmolar solutions of a variety of electrolytes and of glucose against solutions of other solutes of the same, one-half, and twice these osmolarities. In the simpler systems the magnitude of the true anomalous osmosis can be predicted semiquantitatively by reference to appropriate single-solute systems. In isoosmolar systems with two electrolytic solutions the anomalous osmotic flow rates may reach 300 microl./cm.(2) hr. and more; systems with electrolytic solutions against solutions of glucose can produce twice this rate. These fluxes are of the same order of magnitude as the liquid transport rates across such living structures as the mucosa of dog gall bladder, ileum, and urinary bladder.

Callicreinの化学的研究 (第4報)

It was shown in Part III of this series, that purification by zone electrophoresis afforded a homogeneous callicrein (product L, 570U/mg.) from hog pancreas. The isoelectric point of this homogeneous callicrein was measured in order to elucidate its physical and chemical properties. The method of paper electrophoretic analysis, reported by Kunkel and Tiselius, which enables measurement of a micro-quantity, was used. Dextran, which is considered to be in uncharged state, was run with callicrein in order to correct the migration distance of callicrein. This result showed that the isoelectric point of homogeneous callicrein obtained from hog pancreas is at around pH 2.4. For staining of dextran, a 1% ethanolic solution of bromphenol blue is used and stained sample is washed by drops of ethanol.

The contributions of normal and anomalous osmosis to the osmotic effects arising across charged membranes with solutions of electrolytes.

The osmotic effect arising across a porous membrane separating the solution of an electrolyte from water (or a more dilute solution) is ordinarily due to both normal osmosis, as it occurs also with non-electrolytes, and to "anomalous" osmosis. It is shown that the normal osmotic component cannot be measured quantitatively by the conventional comparison with a non-electrolytic reference solute. Anomalous osmosis does not occur with electroneutral membranes. Accordingly, with membranes which can be charged and discharged reversibly (without changes in geometrical structure), such as many proteinized membranes, the osmotic effects caused by an electrolyte can be measured both when only normal osmosis arises (with the membrane in the electroneutral state) and when normal as well as anomalous osmosis occurs (with the membrane in a charged state). The difference between these two effects is the true anomalous osmosis. Data are presented on the osmotic effects across an oxyhemoglobin membrane in the uncharged state at pH 6.75 and in two charged states, positive at pH 4.0 and negative at pH 10.0, with solutions of a variety of electrolytes using a concentration ratio of 2:1 over a wide range of concentrations. The rates of the movement of liquid across the membrane against an inconsequentially small hydrostatic head are recorded instead of, as conventional, the physiologically less significant pressure rises after a standard time.

Metal and hydrogen-ion binding properties of cycloserine

1. 1. Evaluation of data from spectral measurements and titration at varied temperature and solvent composition show that cycloserine in neutral aqueous solutions exists as a zwitterion. These measurements are in full agreement with the results of previous investigators (1, 2). In organic solvents an increasing proportion of the molecule is present in the neutral uncharged state. 2. 2. Cycloserine exhibits appreciable binding avidity for certain bivalent metallic cations. Under the experimental conditions employed, chelate compounds containing two residues of antibiotic per metal ion were formed. The order of binding strength is CU ++ > Zn ++ > CO ++. The binding of Fe ++, Mn ++, Mg ++, and Fe +++ was too weak to be measured. 3. 3. The decreased stability of chelates of cycloserine contrasted to those of serine is concluded to be mainly a consequence of the unfavorable steric relationship of the ligands contributed by the antibiotic.

Negative Ion Emission from Oxide-Coated Cathodes: II

The present paper describes a detailed study of negative ion emission processes from oxide cathodes during all stages of cathode life, using two types of mass spectrometer having oxide cathode sources. The main ions found were those of mass numbers 12, 16, 26, 27, 32, 35, 37, 42 and 43. A retarding potential method was employed to determine energy distributions of all the ions, and special attention was paid to ions emitted during activation, it being found that any oxygen evolved during activation was in an uncharged state. Variations in ion emission due to cathode temperature and applied field were also studied.

The electrostatic free energy of polyelectrolyte solutions. I. Randomly kinked macromolecules

Abstract(1) The electrostatic free energy of randomly kinked, ionized, macromolecules was calculated for polyelectrolyte solutions of finite ionic strenght. A detailed analysis of the charging process and the reference state of the free energy is given. The mutual electrostatic repulsion of the fixed charges on the macromolecule is the main part of the electrostatic free energy. Its calculation is based on two main assumptions: the validity of Kuhn's statistics and of Debye's approximation. (2) The electrostatic contribution per macromolecule to the free energy of the solution is found to be Fe = (v2ϵ2/Dh)ln {1 + (6h/κh)}, where v is the number of charged groups per polymolecule, ϵ the unit of charge, D the dielectric constant, κ Debye's inverse radius, based on the number of free ions in solution, h the end‐to‐end distance of the charged molecule, and h0 the corresponding end‐to‐end distance in and uncharged reference state. (3) Activity coefficients of free ions in polyelectrolyte solutions have been derived from the theory. The calculated values compare favorably with the activity coefficients from measurements on Donnan distribution of salt.

The dimensions of charged long chain molecules in solutions containing electrolytes

AbstractIf a long chain molecule in a solution carries electric charges, the statistical coil is inflated, and the average square of the distance between the ends of the chain is larger than in the uncharged state. For a number of properties the determining factor is the value of ∑k (r2k)av, where rk is the distance between the k'th link in the molecule and the centre of gravity. This quantity is proportional to the square of the effective radius and is related to the square of the distance between the ends by a simple formula (section 2), provided the radius of the coil is small compared with the length of the extended chain.In section 3 the electrical free energy of the molecule is derived as a function of effective radius on the assumption that no electrolytes are present. This free energy determines in its turn the average dimensions of the coil.In section 4 a similar theory is developed for charged polymer molecules in the presence of electrolytes. The change of the effective radius with the charge on the polymer and the concentration of the electrolytes is calculated. In the limit of high electrolyte content the equilibrium between the interior and the exterior of the polymer coil may be considered as a Donnan equilibrium.

Nature of the Nuclear Field

AN attempt to explain neutron-proton interaction made by Yukawa1 in 1935 has been brought to general notice2,3 in connexion with the new experimental evidence for the existence of a 'heavy electron'4,5,6. In 1935, Hideki Yukawa proposed that the force holding the atomic nucleus together resulted from the exchange of a new particle several hundred times heavier than an electron. In consecutive Letters to Nature in 1938, Kemmer and Bhabha developed Yukawa's theory further and proposed that the Yukawa particle, in Kemmer's words, "has a charged and an uncharged state"; the latter, said Bhabha, could "explain the close-range proton-proton interaction". Kemmer added that "its relation to experiment is admittedly quite uncertain" — in 1937 the newly discovered muon had been misidentified as the Yukawa particle. But later the situation became clear: Yukawa's particle was in fact the π meson, or pion. The charged members of the pion family were discovered in 1947 [see Nature 159, 186–190 (1947) & Nature 160, 453–456 (1947)]; Bhabha and Kemmer were proved right when, at Berkeley in 1950, the neutral pion became the first unstable particle to be discovered using an accelerator.

Nuclear Forces, Heavy Electrons and the β-Decay

WE have generalized a theory put forward by Yukawa1 showing that nuclear forces can be explained by assuming the existence of new particles of mass about two hundred times that of the electron. Our theory is relativistically invariant, and in its present form gives results which we believe are of actual significance for cosmic ray and nuclear phenomena. In 1935, Hideki Yukawa proposed that the force holding the atomic nucleus together resulted from the exchange of a new particle several hundred times heavier than an electron. In consecutive Letters to Nature in 1938, Kemmer and Bhabha developed Yukawa's theory further and proposed that the Yukawa particle, in Kemmer's words, "has a charged and an uncharged state"; the latter, said Bhabha, could "explain the close-range proton-proton interaction". Kemmer added that "its relation to experiment is admittedly quite uncertain" — in 1937 the newly discovered muon had been misidentified as the Yukawa particle. But later the situation became clear: Yukawa's particle was in fact the π meson, or pion. The charged members of the pion family were discovered in 1947 [see Nature 159, 186–190 (1947) & Nature 160, 453–456 (1947)]; Bhabha and Kemmer were proved right when, at Berkeley in 1950, the neutral pion became the first unstable particle to be discovered using an accelerator.

Societies and Academies

EDINBURGH Royal Society, July 19.—Mr. Robert Gray, Vice-President, in the chair.—The Right Hon. Lord Rayleigh communicated a paper on the colours of thin plates. He has laid down on Maxwell's triangle of colours a curve representing the variation of the colours of thin plates as the thickness of the plates increases.—Prof. Dr. Fr. Meyer communicated a paper on algebraic knots.—Prof. Tait described Amagat's “manomètre à pistons libres.”—Prof. C. G. Knott communicated a paper on the electrical properties of hydrogenised palladium. This paper contains the results of experiments on the resistance and thermo-electric properties of hydrogenium or hydrogenised palladium. Up to a temperature of about 200° C. no special peculiarity is noticeable; but at that temperature, or a little higher, hydrogen begins to escape from the wire, and this causes the particular specimen of hydrogenium to recover partially, if not wholly, its pure palladium characteristics. It is known that the resistance of a palladium wire charged with hydrogen at ordinary atmospheric temperatures increases at a rate almost strictly proportional to the amount of charge. The fame law seems to hold at all temperatures up to 150° C., and in such a way that the total increase of resistance of a given palladium wire for a given rise of temperature is nearly the same at all charges; or the temperature-coefficient for any particular specimen of hydrogenised wire is practically inversely proportional to the resistance as compared with the resistance of the wire in its pure uncharged state. Just before the hydrogen begins to escape, the resistance begins to increase somewhat more rapidly than at lower temperatures; and this peculiarity is more marked in the specimens of higher charge. When once the hydrogen begins to escape, the resistance begins to fall off rapidly as the temperature rises to 300° C. At this temperature the wire cannot be distinguished from pure palladium. In the thermo-electric experiments, peculiar irregularities appear at the higher temperatures, which seem to be due to the fact that the hydrogenium wire is unequally heated, and that the hydrogen, which is almost completely driven out of the heated portion of the wire, returns partially as the wire is cooled down again. In all cases at temperatures below 150° C., the current is from pure palladium to hydrogenium through the hot junction, is probably proportional to the difference of temperature in each case, and is greater for the greater charge. Thermo-electrically, fully saturated hydroge nium lies between iron and copper at ordinary atmospheric temperatures. On the thermo-electric diagram the hydrogeniums of different charge are represented (up to a temperature of 150° C.) by a series of straight lines parallel to palladium, whose thermoelectric powers at 0° C. range roughly from −600 (pure palladium) to + 1400 (saturated hydrogenium) expressed in C.G.S. units. (Compare Everett's “Units and Physical Constants,” p. 151.) In other words, the electromotive force in a circuit of palladium:and saturated hydrogenium, the temperatures of the junctions being o° C. and 100° C., is 20 X 104 C.G.S. units, or.002 volts. The thermo-electric peculiarities of hydrogenium may be prettily shown by the following simple experiment. Let a palladium wire, by immersion to half its length in the electrolytic cell, be hydrogenised throughout that half length. Attach the ends of this seeming single uniform wire to the terminals of a galvanometer, and let a flame be allowed to play gently at the central point of the wire. A large current is at once obtained, which grows to a maximum, and then diminishes to zero as the tem perature rises to a red heat. There is no such current during cooling. This spurious neutral point is due to the hydrogen being driven out of the heated portion, partly, no doubt, into the contiguous colder portions. By following up with the flame the ever-shifting point of separation between the charged and uncharged portions, we may repeat the experiment indefinitely until the hydrogen is all driven out of the wire, or until the odistribution of hydrogen has become fairly uniform.—Mr. Thomas Andrews communicated a paper on the electro-chemical reactions between metals and fused salts.—Mr. H. N. Dickson communicated a paper on the hygrometry of Ben Nevis and the Scottish Marine Station.—Mr. J. T. Morrison read a paper on the temperature of Loch Lomond and Loch Katrine during winter and spring; also, a note on the surface temperature near a tidal race.—Mr. John Aitken gave further remarks on dew.— Prof. J. B. Haycraft gave a communication on the nature of the objective cause of sensation.