bluuebunny/crossref_metadata_2025_split huggingface dataset:
CRYSTALLINE TRYPSIN
Authors: Northrop John H. 
Published: May 2004

1. If dilute solutions of purified trypsin of low salt concentration at pH from 1 to 7 are heated to 100°C. for 1 to 5 minutes and then cooled to 20°C. there is no loss of activity or formation of denatured protein. If the hot trypsin solution is added directly to cold salt solution, on the other hand, all the protein precipitates and the supernatant solution is inactive.
2. The per cent of the total protein and activity present in the soluble form decreases from 100 per cent to zero as the temperature is raised from 20°C. to 60°C. and increases again from zero to 100 per cent as the solution is cooled from 60°C. to 20°C. The per cent of the total protein present in the soluble (native) form at any one temperature is nearly the same whether the temperature is reached from above or below.
3. If trypsin solutions at pH 7 are heated for increasing lengths of time at various temperatures and analyzed for total activity and total protein nitrogen after cooling, and for soluble activity and soluble (native) protein nitrogen, it is found that the soluble activity and soluble protein nitrogen decrease more and more rapidly as the temperature is raised, in agreement with the usual effects of temperature on the denaturation of protein. The total protein and total activity, on the other hand, decrease more and more rapidly up to about 70°C. but as the temperature is raised above this there is less rapid change in the total protein or total activity and at 92°C. the solutions are much more stable than at 42°C.
4. Casein and peptone are not digested by trypsin at 100°C. but when this digestion mixture is cooled to 35°C. rapid digestion occurs. A solution of trypsin at 100°C. added to peptone solution at zero degree digests the peptone much less rapidly than it does if the trypsin solution is allowed to cool slowly before adding it to the peptone solution.
5. The precipitate of insoluble protein obtained from adding hot trypsin solutions to cold salt solutions contains the S-S groups in free form as is usual for denatured protein.
6. The results show that there is an equilibrium between native and denatured trypsin protein the extent of which is determined by the temperature. Above 60°C. the protein is in the denatured and inactive form and below 20°C. it is in the native and active form. The equilibrium is attained rapidly. The results also show that the formation of denatured protein is proportional to the loss in activity and that the re-formation of native protein is proportional to the recovery of activity of the enzyme. This is strong evidence for the conclusion that the proteolytic activity of the preparation is a property of the native protein molecule.
CRYSTALLINE TRYPSIN
Authors: Northrop John H. 
Published: May 2004

The rate of digestion, as determined by the increase in non-protein nitrogen or formol titration, of casein, gelatin, and hemoglobin with crystalline trypsin preparations increases nearly in proportion to the concentration of protein, but with crude pancreatic extract the rate of digestion becomes independent of the protein concentration in concentrations of more than 2.5 per cent. With both enzymes the rate of digestion of mixtures of 5 per cent casein and gelatin is greater than would be expected from the point of view of a compound between enzyme and substrate. The rate of digestion of 5 per cent casein in the presence of 5 per cent gelatin is exactly the same as that of 5 per cent casein alone. This result is obtained with both enzymes. The digestion of casein with crude trypsin follows the course of a monomolecular reaction quite closely while with purified trypsin the velocity constant decreases as the reaction proceeds. In the case of hemoglobin the monomolecular velocity constant decreases with both purified and crude enzyme.
When the reaction is followed by changes in the viscosity of the solution the abnormal effect of changing substrate concentration disappears and the reaction is in fair agreement with the monomolecular equation. The results as a whole indicate that the abnormalities of the reaction are due to the occurrence of several consecutive reactions rather than to the formation of a substrate enzyme compound.
ON THE RATE OF OXYGEN CONSUMPTION BY FERTILIZED AND UNFERTILIZED EGGS
Authors: Whitaker D. M. 
Published: May 2004

1. Unfertilized eggs of Chaetopterus consume about 2.4 mm.3 O2 per hour per 10 mm.3 eggs at 21°C.
2. In the 1st hour after fertilization, the fertilized eggs consume oxygen at about 53 or 54 per cent of this rate, which is about 1.3 mm.3 O2 per hour per 10 mm.3 eggs at 21°C.
3. For the first 6 hours after fertilization, at 21°C., the curve of the rate of oxygen consumption is slightly asymmetrically sigmoid. The prefertilization rate is regained between 4½ and 5 hours after fertilization. Soon after 6 hours, ciliary activity begins, and the rate of oxygen consumption rises rapidly.
4. The unfertilized eggs of Arbacia punctulata consume about 0.36–0.5 mm.3 O2 per hour per 10 mm.3 eggs at 21°C. The absolute determination is difficult as these eggs are highly sensitive to shaking in the manometer vessels, and these difficulties are discussed.
5. The fertilized eggs of Arbacia punctulata consume oxygen at the rate of about 2.0 mm.3 O2 per hour per 10 mm.3 21°C. At 1 hour after fertilization the rate is already rising.
6. A comparison of the absolute rates of oxygen consumption, and the changes in rate at fertilization of these and a number of other eggs, together with a theoretical discussion, and a discussion of discrepancies in measurements on the eggs of Arbacia punctulata, is contained in the fifth paper of this series (21).
OSMOTIC RELATIONSHIPS IN THE HEN'S EGG
Authors: Johlin J. M. 
Published: May 2004

Data have been given to illustrate the difficulty of obtaining consistent freezing point data with a viscous fluid such as the yolk of the hen's egg and a technique has been described for obtaining reproducible and accurate results consistently. Further freezing point data have been given which were obtained with both fertile and unfertile hen's eggs by the use of a freezing point method previously described by the writer. These data show that there is a pronounced difference between the freezing points of the yolk and the white in contrast to data obtained by the use of the same method by Howard who found the freezing points of the yolk and the white to be the same.
It was shown by freezing point determinations that even in a mixture of yolk and white osmotic equilibrium is slowly arrived at. This again emphasizes the fact established by Smith and Shepherd that since osmotic equilibrium between yolk and white is slowly arrived at, the postulation of a vital activity at the yolk membrane is unnecessary, since the steady state previously postulated need not be assumed to exist.
THE CHARACTERISTICS OF ULTRAFILTRATES OF PLASMA
Authors: Ingraham Raymond C. , Lombard Charles , Visscher Maurice B. 
Published: May 2004

1. Calculations from the Fick diffusion law are shown to predict that membrane equilibria should be established during the course of ultrafiltration.
2. It is shown that the chloride ion is more concentrated and the sodium ion less concentrated in the ultrafiltrate than in the plasma from which the ultrafiltrate was derived.
3. It has been found that by increasing the base bound by protein through a reduction in the bicarbonate content the difference between the plasma concentration and the ultrafiltrate concentration for the several ions studied increases.
4. Calculations from the Donnan equation as to the magnitude of the change in base bound by protein at differing hydrogen ion concentrations are in substantial agreement with the observed values, thus rendering it probable that the membrane equilibrium effect is responsible for the change in distribution ratios observed.
5. It is pointed out that the observed difference in the distribution ratio of cations from that of the chloride anion is probably to be explained by the influence of protein in lowering the activity coefficient of cations when on the alkaline side of the isoelectric point.
6. It is pointed out that account must be taken of these observations in any consideration of the rôle of ultrafiltration in the production of any secretion or body fluid.
THE EFFECT OF CYANIDE AND OF VARIATION IN ALKALINITY ON THE OXIDATION-REDUCTION POTENTIAL OF THE HEMOGLOBIN-METHEMOGLOBIN SYSTEM
Authors: Barnard Robert D. 
Published: May 2004

The potentiometric method was applied to the study of the influence of cyanide and of hydroxyl ion on methemoglobin. Both of these ions appear to combine with the iron of the methemoglobin molecule and reduce its oxidant activity. From the magnitude of the effect produced by cyanide and by variation in pH on the oxidation-reduction potential of the methemoglobin-hemoglobin system, it is concluded that cyanmethemoglobin and alkaline methemoglobin are undissociated ferric compounds, the first with cyanide and the second with hydroxyl.
Electronic formulas, based on the electrical properties of the hemoglobin derivatives, are suggested.
ELECTRICAL RESPONSES FROM THE LATERAL-LINE NERVES OF CATFISH. I
Authors: Hoagland Hudson 
Published: May 2004

1. Records of impulses from the lateral-line nerves of catfish show that the lateral-line organs are in a state of continuous activity, producing a massive discharge of impulses.
2. The discharge may be increased during the direct application of pressure on the skin over the lateral-line canal, by ripples in the water, by irregular currents of water, and by movements of the fish's trunk.
3. The asynchronously discharging lateral-line organs respond to vibratory stimuli from tuning-forks by getting into phase with each other and by beating synchronously at frequencies ranging from 20 to 70 per second. The frequency of beating for a given preparation is independent of the frequency of the tuning-fork for the fork frequencies of 100, 200, and 250 double vibrations which were used.
4. The continuous discharge of the lateral-line system is markedly changed by alteration of temperature. The frequency declines on lowering the temperature and rises on increasing it. Spinal and facial nerves in the catfish fail to yield nerve impulses in response to changes of the skin temperature between 0° and 28°C., although the intact animal is known to be sensitive to temperature differences.
5. The action of the lateral-line system of Ameiurus in inhibiting responses initiated through the skin and ears (Parker and Van Heusen, 1917) is discussed in the light of the present experiments.
DEVELOPMENT OF THE EGG OF THE MACKEREL AT DIFFERENT CONSTANT TEMPERATURES
Authors: Worley Leonard G. 
Published: May 2004

1. Mackerel egg development was followed to hatching at constant temperatures of 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, and 24°C. Experiment showed that typical development could be realized only between 11° and 21°.
2. The length of the developmental period increases from 49.5 hours to 207 hours when the temperature is lowered from 21° to 10°C.
3. The calculated µ for the development of the mackerel egg is about 19,000 at temperatures above 15° and approximately 24,900 for temperatures below 15°C. 15° is, apparently, a critical temperature for this process.
4. The calculated values of µ for eight stages of development preceding hatching, i.e. 6 somites, 12 somites, 18 somites, 24 somites, three-quarters circles, four-fifths circles, five-sixths circles, and full circles, are essentially the same as the µ's for hatching, indicating that the rate of differentiation up to hatching is governed by one process throughout. Critical temperatures for these stages approximate 15°.
5. The total mortality during the incubation period was least at 16°C. where it amounted to 43 per cent. At temperatures above and below this there was a steady increase in the percentage of mortality which reached 100 per cent at 10° and 21°.
PHOTIC STIMULATION AND LEG MOVEMENTS IN THE CRAYFISH
Authors: Kropp B. , Enzmann E. V. 
Published: May 2004

When Cambarus clarkii is exposed to a source of light so that both eyes are equally illuminated, leg movements of the two sides are equal in frequency and amplitude.
On covering one eye and exposing the uncovered eye to light, leg movements on the side of the uncovered eye are more frequent and are of greater amplitude than on the side of the covered eye. On covering the exposed eye also the leg movements on the two sides again tend to become equal in frequency and amplitude.
When one eye is lost and the other remains functional, the leg movements on the side of the lost eye will be similar to those on the side of a normal, covered eye.
THE MODIFICATION OF ANTIBODIES BY FORMALDEHYDE
Authors: Mudd Stuart , Joffe Eleanore W. 
Published: May 2004

Certain strains of bacteria which have only minimal zeta potentials over a wide range of pH, and upon which surface deposits can be formed, afford a favorable means of studying certain chemical and physical properties of the surface deposits.
Films of specific antibody-globulin upon these bacteria possess basic groups which can combine with formaldehyde. Combination of these groups with HCHO under the conditions of the present experiments shifts the isoelectric point of the sensitizing film toward the acid side by about 0.6 to 0.8 pH unit, and reduces the agglutinating tendency of the sensitizing film.
Antibodies may be formalinized before combination with antigen without marked change in their specific combining affinities. The properties of the sensitizing films are similar whether formol treatment occurs before or after the antigen-antibody combination.
The nature of the basic groups has been discussed.
THE COUPLED REDOX POTENTIAL OF THE LACTATE-ENZYME-PYRUVATE SYSTEM
Authors: Baumberger J. Percy , Jürgensen J. J. , Bardwell Kathleen 
Published: May 2004

1. The term "coupled redox potential" is defined.
2. The system lactic ion
See PDF for Equation
pyruvic ion + 2H+ + 2e is shown
to be reversible (when the enzyme is lactic acid dehydrogenase) and its coupled redox potential between pH 5.2 and 7.2 at 32°C. is:
See PDF for Equation
3. The free energy of the reaction:
lactic ion (1m) → pyruvic ion (1m) = -ΔF = –14,572.
4. The standard free energy of formation (ΔF298) of pyruvic acid (l) is estimated at –108,127. This is merely an approximation as some necessary data are lacking.
5. The importance of coupled redox potentials as a factor in the regulation of the equilibrium of metabolites is indicated.
CRITICAL FREQUENCY OF FLICKER AS A FUNCTION OF INTENSITY OF ILLUMINATION FOR THE EYE OF THE BEE
Authors: Wolf Ernst 
Published: May 2004

The bee's characteristic response to a movement of its visual field is used for the study of the relation between critical frequency of flicker and illumination. The critical flicker frequency varies with illumination in such a way that with increasing flicker frequency the intensity of illumination must be increased to produce a threshold response in the bee.
The illuminations required to give a response in a bee at different flicker frequencies closely correspond to the intensities for threshold response in visual acuity tests. This is due to the different thresholds of excitability of the elements of the ommatidial mosaic.
An analysis of the variation of the values for threshold intensities at the several flicker frequencies shows that the variation depends upon flicker frequency and upon the number of elements functioning at different intensities.
THE EFFECT OF ULTRAVIOLET LIGHT ON PHOTOSYNTHESIS
Authors: Arnold William 
Published: May 2004

1. An unidentified unit in the mechanism of the photosynthesis of Chlorella pyrenoidosa is rendered inactive by the absorption of one quantum of ultraviolet light (2537 Å wave length).
2. The same irradiation has no effect on the normal respiration of Chlorella pyrenoidosa. Experiments have not yet been made on the respiration inhibitable by HCN.
3. No chemical change was detected in the chlorophyll extracted from irradiated cells.
THE ESTIMATION OF TRYPSIN WITH HEMOGLOBIN
Authors: Anson M. L. , Mirsky A. E. 
Published: May 2004

The formation from hemoglobin of split products not precipitable by trichloracetic acid is taken as a measure of tryptic activity. The split products are estimated colorimetrically.
Many measurements of tryptic activity can be made in a short time and different samples of hemoglobin yield the same results.
THE CONVERSION OF FAT TO CARBOHYDRATE IN THE GERMINATING CASTOR BEAN
Authors: Daggs Ray G. , Halcro-Wardlaw H. S. 
Published: May 2004

The combustion respiratory quotients of castor beans germinated to various stages, depending upon the length of the hypocotyl, were determined by means of a modified oxycalorimeter.
After germination was well started, the respiratory quotient of the combusted germinated seed increased as the stage of germination increased, indicating a change from an oxygen-poor to an oxygen-rich substance, probably fat to sugar.
The accuracy of the method was checked by organic combustions.
The seat of formation of the oxygen-rich substance is in the endosperm.
BACTERIAL CELL METABOLISM UNDER ANAEROBIC CONDITIONS
Authors: Walker H. H. , Winslow C.-E. A. , Mooney M. Grace 
Published: May 2004

Escherichia coli has been cultivated in a peptone water medium saturated continuously with nitrogen by use of a gas train so as to produce anaerobic conditions. Under these circumstances growth was greatly inhibited. Cultures which originally contained 11 million bacteria per cc. showed on the average only 32 million after 5 hours (as compared with 655 million in similar cultures saturated with air).
The metabolic activity of the cells in such a culture was greatly reduced by the anaerobic conditions. It actually fell off from 42 mg. x 10–11 per cell per hour during the 1st hour to 27 mg. during the 2nd hour and rose only to a maximum of 68 during the 3rd hour. Similar cultures saturated with air showed a rise from 37 mg. x 10–11 during the 1st hour to 123 during the 2nd hour.
The addition of glucose to the medium, under aerobic conditions, has been shown in previous studies to cause only a slight increase in bacterial numbers (861 instead of 655 million after the 5th hour). In the cultures aerated with nitrogen, the addition of glucose has no effect during the first hours. There is again a long lag period and a reduced metabolic rate. After the 2nd hour, however, a wholly different phenomenon manifests itself. The bacterial population increases more rapidly than in the anaerobic peptone medium (reaching a maximum of 142 million after 5 hours). This growth is accompanied by an enormous increase in the rate of CO2 yield, which reaches 211 mg. x 10–11 per cell per hour during the 4th hour (nearly double the maximum values recorded under aerobic conditions). The same phenomenon is, of course, illustrated by the enormous yield of CO2 produced by the action of fermenting organisms in carbohydrate media recorded by Anderson (1924) and other students of the obligate anaerobes. We have here, however, a somewhat striking illustration of the distinct type of metabolic activity manifested by a facultative organism under anaerobic conditions in the presence of sugar measured on a cell-per-hour basis. This is a quantitative illustration of the "life without air" described by Pasteur.
A PHOTOELECTRIC DENSITOMETER FOR USE WITH SUSPENSIONS
Authors: Stier T. J. B. , Arnold W. , Stannard J. N. 
Published: May 2004

A device for quickly and accurately measuring the population density of a suspension of microorganisms, permitting the preparation of yeast suspensions of known density to within 1 per cent error, was constructed with two Visitron photoelectric cells, a single light of high intensity and a good Wheatstone bridge for balancing the currents from the two photoelectric cells. A large Pyrex milk culture tube holding the suspension is placed in the path of one beam of light coming through a small longitudinal slit and thence to one photocell; a second similar slit directs another beam of light upon the second photocell, thus causing dissimilar currents to flow, the ratio of whose magnitudes may be measured by the bridge resistances. A relation between these currents and the relative light intensities is shown, and the one significant unmeasurable variable (the characteristic constant of a photocell) is practically eliminated by the use of a method of ratios.
After careful standardization of technique the apparatus proved more accurate than other methods available for the purpose indicated. In rapid use its accuracy may be put safely at 1 per cent for measuring the densities of cultures of approximately the same age and composed of cells having comparable optical characteristics.
THE REVERSIBLE INACTIVATION OF BACTERIOPHAGE BY BICHLORIDE OF MERCURY
Authors: Krueger A. P. , Baldwin D. M. 
Published: May 2004

1. The complete inactivation of antistaphylococcal phage by HgCl2 (2.8 per cent for 216 hours) can be reversed by precipitation of Hg++ with restoration of the phage to its original titre.
2. This behavior seems more compatible with the known properties of certain enzymes than with those of living protoplasm.
THE KINETICS OF PENETRATION
Authors: Osterhout W. J. V. , Kamerling S. E. 
Published: May 2004

A model is described which throws light on the mechanism of accumulation. In the model used an external aqueous phase A is separated by a non-aqueous phase B (representing the protoplasm) from the artificial sap in C. A contains KOH and C contains HCl: they tend to mix by passing through the non-aqueous layer but much more KOH moves so that most of the KCl is formed in C, where the concentration of potassium becomes much greater than in A. This accumulation is only temporary for as the system approaches equilibrium the composition of A approaches identity with that of C, since all the substances present can pass through the non-aqueous layer. Such an approach to equilibrium may be compared to the death of the cell as the result of which accumulation disappears.
During the earlier stages of the experiment potassium tends to go in as KOH and at the same time to go out as KCl. These opposing tendencies do not balance until the concentration of potassium inside becomes much greater than outside (hence potassium accumulates). The reason is that KCl, although its driving force be great, moves very slowly in B because its partition coefficient is low and in consequence its concentration gradient in B is small. This illustrates the importance of partition coefficients for penetration in models and in living cells. It also indicates that accumulation depends on the fact that permeability is greater for the ingoing compound of the accumulating substance than for the outgoing compound.
Other things being equal, accumulation is increased by maintaining a low pH in C. Hence we may infer that anything which checks the production of acid in the living cell may be expected to check accumulation and growth.
This model recalls the situation in Valonia and in most living cells where potassium accumulates as KCl, perhaps because it enters as KOH and forms KA in the sap (where A is an organic anion). In some plants potassium accumulates as KA but when HCl exists in the external solution it will tend to enter and displace the weaker acid HA (if this be carbonic it can readily escape): hence potassium may accumulate to a greater or less extent as KCl.
Injury of the cell may produce a twofold effect, (1) increase of permeability, (2) lessened accumulation. The total amount of electrolyte taken up in a given time will be influenced by these factors and may be greater than normal in the injured cell or less, depending somewhat on the length of the interval of time chosen.