bluuebunny/crossref_metadata_2025_split huggingface dataset:
DOES THE KINETICS OF TRYPSIN DIGESTION DEPEND ON THE FORMATION OF A COMPOUND BETWEEN ENZYME AND SUBSTRATE
Authors: Northrop John H. 
Published: May 2004

1. The velocity of hydrolysis of gelatin by trypsin increases more slowly than the gelatin concentration and finally becomes nearly independent of the gelatin concentration. The relative velocity of hydrolysis of any two substrate concentrations is independent of the quantity of enzyme used to make the comparison.
2. The rate of hydrolysis is independent of the viscosity of the solution.
3. The percentage retardation of the rate of hydrolysis by inhibiting substances, is independent of the substrate concentration.
4. There is experimental evidence that the enzyme and inhibiting substance are combined to form a widely dissociated compound.
5. If the substrate were also combined with the enzyme, an increase in the substrate concentration should affect the equilibrium between the enzyme and the inhibiting substance. This is not the case.
6. The rate of digestion of a mixture of casein and gelatin is equal to the sum of the rates of hydrolysis of the two substances alone, as it should be if the rate is proportional to the concentration of free enzyme. This contradicts the saturation hypothesis.
7. If the reaction is followed by determining directly the change in the substrate concentration, it is found that this change agrees with the law of mass action; i.e., the rate of digestion is proportional to the substrate concentration.
EFFECT OF COCAINE ON THE GROWTH OF LUPINUS ALBUS. A CONTRIBUTION TO THE COMPARATIVE PHARMACOLOGY OF ANIMAL AND PLANT PROTOPLASM
Authors: Macht David I. , Livingston Marguerite B. 
Published: May 2004

1. The effects of cocaine and its decomposition products were studied on the growth of the young roots of Lupinus albus.
2. The results obtained were compared with similar experiments on animal tissues.
3. It was found that, while cocaine is the most toxic of these compounds studied for animal tissues, it was of comparatively low toxicity in respect to its effect on the growth of roots. On the other hand, sodium benzoate, being practically non-toxic for animals, was the most toxic of the compounds studied for the plant roots.
THE COLLOIDAL BEHAVIOR OF EDESTIN
Authors: Hitchcock David I. 
Published: May 2004

1. It has been shown by titration experiments that the globulin edestin behaves like an amphoteric electrolyte, reacting stoichiometrically with acids and bases.
2. The potential difference developed between a solution of edestin chloride or acetate separated by a collodion membrane from an acid solution free from protein was found to be influenced by salt concentration and hydrogen ion concentration in the way predicted by Donnan's theory of membrane equilibrium.
3. The osmotic pressure of such edestin-acid salt solutions was found to be influenced by salt concentration and by hydrogen ion concentration in the same way as is the potential difference.
4. The colloidal behavior of edestin is thus completely analogous to that observed by Loeb with gelatin, casein, and egg albumin, and may be explained by Loeb's theory of colloidal behavior, which is based on the idea that proteins react stoichiometrically as amphoteric electrolytes and on Donnan's theory of membrane equilibrium.
THE ELIMINATION OF DISCREPANCIES BETWEEN OBSERVED AND CALCULATED P.D. OF PROTEIN SOLUTIONS NEAR THE ISOELECTRIC POINT WITH THE AID OF BUFFER SOLUTIONS
Authors: Loeb Jacques 
Published: May 2004

1. It had been noticed in the previous experiments on the influence of the hydrogen ion concentration on the P.D. between protein solutions inside a collodion bag and aqueous solutions free from protein that the agreement between the observed values and the values calculated on the basis of Donnan's theory was not satisfactory near the isoelectric point of the protein solution. It was suspected that this was due to the uncertainty in the measurements of the pH of the outside aqueous solution near the isoelectric point. This turned out to be correct, since it is shown in this paper that the discrepancy disappears when both the inside and outside solutions contain a buffer salt.
2. This removes the last discrepancy between the observed P.D. and the P. D. calculated on the basis of Donnan's theory of P.D. between membrane equilibria, so that we can state that the P.D. between protein solutions inside collodion bags and outside aqueous solutions free from protein can be calculated from differences in the hydrogen ion concentration on the opposite sides of the membrane, in agreement with Donnan's formula.
ELECTRICAL CHARGES OF COLLOIDAL PARTICLES AND ANOMALOUS OSMOSIS
Authors: Loeb Jacques 
Published: May 2004

1. When solutions of KCl, NaCl, or LiCl are separated from water without salt by a collodion-gelatin membrane and when the pH of both salt solution and water are on the acid side of the isoelectric point of gelatin, water diffuses from the side of pure water into the salt solution at a rate increasing inversely with the radius of the cations.
2. The adsorption theory would lead us to assume that this influence of the cations is due to an increase of the P.D. between the liquid and the membrane inside the pores of the gelatin film of the membrane, but direct measurements of this P.D. contradict such an assumption, since they show that the influence of the three salts on this P.D. is identical at pH 3.0.
3. It is found, however, that the P.D. across the membrane is affected in a similar way by the three cations as is the transport of water through the membrane.
4. This P.D. across the membrane varies inversely as the relative mobility of the three cations which suggests that the influence of the three cations on the diffusion of liquid through the membrane is partly if not essentially due to a diffusion potential.
THE STABILITY OF BACTERIAL SUSPENSIONS
Authors: Northrop John H. , De Kruif Paul H. 
Published: May 2004

1. The addition of proteins or serum to suspensions of bacteria, (Bacillus typhosus or rabbit septicemia) at different pH widens the acid agglutination zone and shifts the isoelectric point to that of the added substance.
2. The amount of serum required to agglutinate is much less near the acid agglutination point of the organisms.
3. The addition of immune serum prevents the salt from decreasing the cohesive force between the organisms, and agglutination therefore is determined solely by the potential, provided excess immune body is present. Whenever the potential is decreased below 15 millivolts the suspension agglutinates.
STUDIES IN THE PHYSICAL CHEMISTRY OF THE PROTEINS
Authors: Cohn Edwin Joseph 
Published: May 2004

1. Two proteins of the globulin type, serum globulin and tuberin, and the protein of milk, casein, have been purified (a) of the other proteins and (b) of the inorganic electrolytes with which they exist in nature. The methods that were employed are described.
2. All three proteins were found to be only very slightly soluble in water in the pure uncombined state. The solubility of each was accurately measured at 25.0° ± 0.1°C. The most probable solubility of the pseudoglobulin of serum was found to be 0.07 gm. in 1 liter; of tuberin 0.1 gm. and of casein 0.11 gm. The methods that were employed in their determination are described.
3. Each protein investigated dissolved in water to a constant and characteristic extent when the amount of protein precipitate with which the solution was in heterogeneous equilibrium was varied within wide limits. The solubility of a pure protein is therefore proposed as a fundamental physicochemical constant, which may be used in identifying and in classifying proteins.
4. The concentration of protein dissolved must be the sum of the concentration of the undissociated protein molecule which is in heterogeneous equilibrium with the protein precipitate, and of the concentration of the dissociated protein ions.
5. The dissociated ions of the dissolved protein give a hydrogen ion concentration to water that is also a characteristic of each protein.
THE MECHANISM BY WHICH TRIVALENT AND TETRAVALENT IONS PRODUCE AN ELECTRICAL CHARGE ON ISOELECTRIC PROTEIN
Authors: Loeb Jacques 
Published: May 2004

1. Experiments on anomalous osmosis suggested that salts with trivalent cations, e.g. LaCl3, caused isoelectric gelatin to be positively charged, and salts with tetravalent anions, e.g. Na4Fe(CN)6, caused isoelectric gelatin to be negatively charged. In this paper direct measurements of the P.D. between gels of isoelectric gelatin and an aqueous solution as well as between solutions of isoelectric gelatin in a collodion bag and an aqueous solution are published which show that this suggestion was correct.
2. Experiments on anomalous osmosis suggested that salts like MgCl2, CaCl2, NaCl, LiCl, or Na2SO4 produce no charge on isoelectric gelatin and it is shown in this paper that direct measurements of the P.D. support this suggestion.
3. The question arose as to the nature of the mechanism by which trivalent and tetravalent ions cause the charge of isoelectric proteins. It is shown that salts with such ions act on isoelectric gelatin in a way similar to that in which acids or alkalies act, inasmuch as in low concentrations the positive charge of isoelectric gelatin increases with the concentration of the LaCl3 solution until a maximum is reached at a concentration of LaCl3 of about M/8,000; from then on a further increase in the concentration of LaCl3 diminishes the charge again. It is shown that the same is true for the action of Na4Fe(CN)6. From this it is inferred that the charge of the isoelectric gelatin under the influence of LaCl3 and Na4Fe(CN)6 at the isoelectric point is due to an ionization of the isoelectric protein by the trivalent or tetravalent ions.
4. This ionization might be due to a change of the pH of the solution, but experiments are reported which show that in addition to this influence on pH, LaCl3 causes an ionization of the protein in some other way, possibly by the formation of a complex cation, gelatin-La. Na4Fe(CN)6 might probably cause the formation of a complex anion of the type gelatin-Fe(CN)6. Isoelectric gelatin seems not to form such compounds with Ca, Na, Cl, or SO4.
5. Solutions of LaCl3 and Na4Fe(CN)6 influence the osmotic pressure of solutions of isoelectric gelatin in a similar way as they influence the P.D., inasmuch as in lower concentrations they raise the osmotic pressure of the gelatin solution until a maximum is reached at a concentration of about M/2,048 LaCl3 and M/4,096 Na4Fe(CN)6. A further increase of the concentration of the salt depresses the osmotic pressure again. NaCl, LiCl, MgCl2, CaCl2, and Na2SO4 do not act in this way.
6. Solutions of LaCl3 have only a depressing effect on the P.D. and osmotic pressure of gelatin chloride solutions of pH 3.0 and this depressing effect is quantitatively identical with that of solutions of CaCl2 and NaCl of the same concentration of Cl.
IONIZING INFLUENCE OF SALTS WITH TRIVALENT AND TETRAVALENT IONS ON CRYSTALLINE EGG ALBUMIN AT THE ISOELECTRIC POINT
Authors: Loeb Jacques 
Published: May 2004

1. While crystalline egg albumin is highly soluble in water at low temperature at the pH of its isoelectric point, it is coagulated by heating. It has long been known that this coagulation can be prevented by adding either acid or alkali, whereby the protein is ionized.
2. It is shown in this paper that salts with trivalent or tetravalent ions, e.g. LaCl3 or Na4Fe(CN)6, are also able to prevent the heat coagulation of albumin at the isoelectric point (i.e. pH 4.8), while salts with a divalent ion, e.g. CaCl2, BaCl4, Na2SO4, or salts like NaCl, have no such effect.
3. This is in harmony with the fact shown in a preceding paper that salts with trivalent or tetravalent ions can cause the ionization of proteins at its isoelectric point and thus give rise to a membrane potential between micellæ of isoelectric protein and surrounding aqueous solution, while the above mentioned salts with divalent and monovalent ions have apparently no such effect.
ON THE INFLUENCE OF AGGREGATES ON THE MEMBRANE POTENTIALS AND THE OSMOTIC PRESSURE OF PROTEIN SOLUTIONS
Authors: Loeb Jacques 
Published: May 2004

1. It is shown that when part of the gelatin in a solution of gelatin chloride is replaced by particles of powdered gelatin (without change of pH) the membrane potential of the solution is influenced comparatively little.
2. A measurement of the hydrogen ion concentration of the gelatin chloride solution and the outside aqueous solution with which the gelatin solution is in osmotic equilibrium, shows that the membrane potential can be calculated from this difference of hydrogen ion concentration with an accuracy of half a millivolt. This proves that the membrane potential is due to the establishment of a membrane equilibrium and that the powdered particles participate in this membrane equilibrium.
3. It is shown that a Donnan equilibrium is established between powdered particles of gelatin chloride and not too strong a solution of gelatin chloride. This is due to the fact that the powdered gelatin particles may be considered as a solid solution of gelatin with a higher concentration than that of the weak gelatin solution in which they are suspended. It follows from the theory of membrane equilibria that this difference in concentration of protein ions must give rise to potential differences between the solid particles and the weaker gelatin solution.
4. The writer had shown previously that when the gelatin in a solution of gelatin chloride is replaced by powdered gelatin (without a change in pH), the osmotic pressure of the solution is lowered the more the more dissolved gelatin is replaced by powdered gelatin. It is therefore obvious that the powdered particles of gelatin do not participate in the osmotic pressure of the solution in spite of the fact that they participate in the establishment of the Donnan equilibrium and in the membrane potentials.
5. This paradoxical phenomenon finds its explanation in the fact that as a consequence of the participation of each particle in the Donnan equilibrium, a special osmotic pressure is set up in each individual particle of powdered gelatin which leads to a swelling of that particle, and this osmotic pressure is measured by the increase in the cohesion pressure of the powdered particles required to balance the osmotic pressure inside each particle.
6. In a mixture of protein in solution and powdered protein (or protein micellæ) we have therefore two kinds of osmotic pressure, the hydrostatic pressure of the protein which is in true solution, and the cohesion pressure of the aggregates. Since only the former is noticeable in the hydrostatic pressure which serves as a measure of the osmotic pressure of a solution, it is clear why the osmotic pressure of a protein solution must be diminished when part of the protein in true solution is replaced by aggregates.
ALTERATION BY DINITROCRESOL OF PATHWAYS FOR GLUCOSE OXIDATION IN EGGS OF ARBACIA PUNCTULATA
Authors: Keltch A. K. , Krahl M. E. , Clowes G. H. A. 
Published: May 2004

1. The C14O2 production by Arbacia eggs and embryos from glucose-1-C14, glucose-2-C14, and glucose-6-C14 has been measured without and with dinitrocresol in the incubation medium. In the absence of the dinitrocresol, the C14O2 production from glucose-1-C14 is more rapid than from glucose-2-C14 and much more rapid than from glucose-6-C14; this, together with previous findings, indicates that glucose is utilized in Arbacia eggs predominantly via the TPN shunt rather than via the aldolase step of the glycolytic pathway. In the presence of the dinitrocresol, C14O2 from glucose-6-C14 approaches that from glucose-1-C14, indicating that, in the presence of this reagent, glucose utilization is diverted from the shunt to the glycolytic pathway.
2. Incorporation of C14 from glucose labelled in the 1-, 2-, or 6- positions into other metabolic products of the eggs and embryos is also inhibited by dinitrocresol, particularly incorporation into the acid-insoluble fraction containing nucleoproteins.
A NEW PHOTOSENSITIVE PIGMENT OF THE EURYHALINE TELEOST, GILLICHTHYS MIRABILIS
Authors: Munz Frederick W. 
Published: May 2004

Retinal extracts have been prepared from dark-adapted mudsuckers by treatment of retinal tissue or of isolated outer segments of the visual cells with digitonin solution. The extracts were examined spectrophotometrically and found to absorb light maximally between the wave lengths of 488 and 510 mµ, depending on the proportion of yellow impurities and light-sensitive pigment present. This photosensitive pigment was shown to be homogeneous by partial bleaching of the extracts with monochromatic light of various wave lengths from 390 to 660 mµ. The mudsucker pigment was specifically demonstrated not to be a mixture of rhodopsin and porphyropsin; the adequacy of the method used to analyze such mixtures was shown by performing a control experiment with an artificial mixture of bullfrog rhodopsin and carp porphyropsin.
Comparison of the hydroxylamine difference spectrum and of the absorption maximum of the purest retinal extract located the mudsucker photosensitive pigment maximum at 512 ± 1 mµ. Extraction of retinal tissue with a fat solvent after exposure to white light gave a preparation which after the addition of antimony chloride reagent developed the absorption band maximal near 664 mµ, which is characteristic of retinene1. If an hour intervened between exposure of the retinal tissue to light and extraction of the carotenoid, the antimony trichloride test gave a color band maximal at 620 mµ, characteristic of vitamin A1. No evidence of retinene2 or vitamin A2 was obtained. The euryhaline mudsucker has, therefore, a photosensitive retinal pigment with an absorption maximum halfway between the peaks of rhodopsins and of porphyropsins and belonging to the retinene1 system characteristic of rhodopsins. The pigment is therefore named a retinene1 pigment 512 of the mudsucker, Gillichthys mirabilis. It is uncertain whether this type of photosensitive pigment will be found in other euryhaline fishes.
ADAPTATION OF BACILLUS MEGATHERIUM TO TERRAMYCIN (OXYTETRACYCLINE)
Authors: Northrop John H. ,   With the Technical Assistance of Marie King
Published: May 2004

B. megatherium cultures contain a few cells per hundred million which are able to grow in the presence of terramycin. Growth of the other cells is inhibited by the antibiotic with the result that the resistant cells overgrow the culture. The resistant cells are present in the culture, without contact with terramycin, and are able to grow in the presence of terramycin, without further modification.
The resistant cells are mutants of sensitive cells.
PROPERTIES OF PHYCOBILINS FROM PORPHYRA NAIADUM
Authors: Airth R. L. , Blinks L. R. 
Published: May 2004

The phycobilin pigments were freshly extracted from Porphyra naiadum in the cold.
At least two types of phycoerythrin (I and II) can be distinguished by electrophoresis, chromatography, and spectral characteristics.
At pH 5.0 phycoerythrin II has a relatively large negative charge, while phycoerythrin I is nearly iso-electric. At pH 7.0, however, phycoerythrin I has the larger negative charge. Mobilities have been calculated by visual measurement of electrophoresis.
Phycoerythrin II can be converted to phycoerythrin I by storing at pH 7.0.
Chromatography indicates at least two types of phycocyanin as well.
RESPIRATORY METABOLISM OF NORMAL AND DIVISIONLESS STRAINS OF CANDIDA ALBICANS
Authors: Ward John M. , Nickerson Walter J. 
Published: May 2004

Respiration of a normal strain of Candida albicans was compared with that of a divisionless mutant which has a biochemical lesion such that metabolically generated hydrogen "spills over," during growth, for non-specific dye reduction. This waste is not at expense of growth, since both strains grow at essentially similar rates, nor at expense of respiration, since the mutant reduces oxygen more rapidly than the normal strain. Respiration in both strains is qualitatively similar, and seemingly unique among highly aerobic organisms in that it is not mediated by cytochrome oxidase. In resting cells of both strains, respiration is not only resistant to, but markedly stimulated by, high concentrations of cyanide, carbon monoxide, and azide. In contrast, growth of these yeasts is inhibited by low concentrations of cyanide and azide.
Cytochrome oxidase could not be detected in cell-free preparations; reduced cytochrome c was not oxidized by such preparations. Cytochrome bands could not be observed in thick cell suspensions treated with reducing agents. However, incorporation of superoptimal levels of zinc and iron into the culture medium resulted in growth of cells possessing distinct cytochrome bands; respiration of these cells remained insensitive to cyanide, monoxide, and azide, and the bands were maintained in a reduced form on oxygenation.
In the divisionless yeast, tetrazolium dyes compete with oxygen for reduction; this is not the case in the normal strain. The firmness with which hydrogen transfer is channeled in the latter for reduction of disulfide bonds (of importance in the division mechanism) and of oxygen, is contrasted with the lack of such control in the mutant.
THE FUNCTION OF THE PROXIMAL SYNAPSES OF THE SQUID STELLATE GANGLION
Authors: Bryant S. H. 
Published: May 2004

In the oxygenated excised squid (Loligo pealii) stellate ganglion preparation one can produce excitation of the stellar giant axons by stimulating the second largest (accessory fiber, Young, 1939) or other smaller preganglionic giant axons. Impulse transmission is believed to occur at the proximal synapses of the stellar giant axons rather than the distal (giant) synapses which are excited by the largest giant preaxon.
Proximal synaptic transmission is more readily depressed by hypoxia and can be fatigued independently of, and with fewer impulses than, the giant synapses. Intracellular recording from the last stellar axon at its inflection in the ganglion reveals both proximal and distal excitatory postsynaptic potentials EPSP's). The synaptic delay, temporal form of the EPSP, and depolarization for spike initiation were similar for both synapses.
If the proximal EPSP occurs shortly after excitation by the giant synapse it reduces the undershoot and adds to the falling phase of the spike. If it occurs later it can produce a second spike. Parallel results were obtained when the proximal EPSP's arrived earlier than the EPSP of the giant synapse.
In fatigued preparations it was possible to sum distal and proximal or two proximal EPSP's and achieve spike excitation.
AN ENZYMATIC ION EXCHANGE MODEL FOR ACTIVE SODIUM TRANSPORT
Authors: Koblick Daniel C. 
Published: May 2004

An enzymatic ion exchange model for active sodium transport is described. Kinetic equations relating net flux to time, and to concentration difference across the actively transporting membrane are derived. The second of these equations is tested, using the isolated frog skin in the "short-circuit" apparatus of Ussing. Reasonable linearity, as predicted by this equation, is observed.
The passive permeability coefficient for Na+, is calculated as 5.3 x 10-4 ± 5.3 x 10-4 cm./hr. If cholinesterase is assumed to be the enzyme responsible for transport, the activity required to account for the observations reported here is 17.7 x 10-4 mmoles/cm.2/hr.