Lapas attēli

Buchner was apparently the first to use litmus media for bacteria, although the ophthalmologist Leber preceded him by three years, employing litmus gelatine to demonstrate acid production by Aspergillus.

Cahen, and not “Cohen (1),” published his paper in the Journal given, in the next volume to that cited. While the citation is not correct as to volume and page, still with the name and Journal given it hardly justifies characterization as “apparently altogether erroneous.

been received of a bottle which was picked up in the Orkney Islands. This bottle, No. 230, was set out on the same day (August 29, 1919) as No. 198 which went to the Azores and was put out about 64 miles to the southeast of it, i.e., 71 miles southeast of Point Lepreaux in the Bay of Fundy. It was picked up on the Island of Papa Westray, one of the northwestern islands of the Orkney group, on January 21, 1921, about one year and five months after it was set out. This bottle probably followed the northern route of the North Atlantic wind drift (“Gulf Stream") as indicated for another bottle recorded previously.”



It thus appears that both of us have been to some extent guilty and the present note is therefore offered in mutual condonation.

The following list of authentic references prior to 1890 was supplied by Professor Novy and each has been confirmed by the undersigned. Leber-Berl. klin. Wchnschr., 1882, 19. 163. H. Buchner-Arch. f. Hyg., 1885, 3, pp. 417,

418, 419. Marpmann-Centralbl. f. d. allgemeine Ge

sundheitspflege; Ergänzungshefte, 1885– 1886, 2, Heft 2, p. 123. (The number appeared in 1886 but the title page of

the volume bears date of 1889.) Weisser-Ztschr. f. Hyg., 1886, 1, p. 334. Cahen-Ibid., 1887, 2, pp. 387, 394. Neisser-Virchow's Archiv. f. pathol. Anat.

u. Physiol., 1887, 110, p. 394. Loeffler-Berl. klin. Wchnschr., 1887, 24, pp.

610, 631. Berhring-Ztschr. f. Hyg., 1889, 6, p. 142;

7, pp. 173, 177. Petruschky-Centralbl. f. Bakteriol., 1889, 6, pp. 628, 657.

Ivan C. HALL

[ocr errors]
[ocr errors]

NEWSPAPER SCIENCE TO THE EDITOR OF SCIENCE: The recent press reports quoting me as saying that I had “ obtained the closest approach to a perfect vacuum ever recorded” are false and without foundation. The daily press copied and added to an item in the Utah Chronicle, a student paper, which itself was inaccurate in saying I had “ perfected the apparatus." The student reporter after seeing in the department of physics a well-known form of vacuum pump wrote the original article without submitting it to me before publication. I am taking this opportunity to deny the statements credited to me by the newspapers which have given me so much undesirable and distasteful publicity.


April 8, 1921

[merged small][merged small][ocr errors][merged small][merged small][merged small]

In all 29 gages are in operation-distributed Bellahouston Park

8.87 as follows: Birmingham 3, London 8, Glas- Botanic Gardens

10.91 gow 9, Southport 2, and 1 each at Kingston, Queens Park

8.01 Malvern, Newcastle, Rochdale, Rothamsted, Richmond Park

12.15 St. Helens, and Sterling. Two more stations are about to operate.

Generally speaking there is evidence of a Full returns have been published in the considerable diminution of summer deposit in Lancet.

practically all the districts. The following data are given in this report: The highest deposit of tar in the London

1. Monthly deposits for the two stations rep- group was in February, the lowest in May; resenting high and low deposits.

while in the Glasgow group the highest was 2. Total solids deposited monthly at all sta- in November and the lowest in September. tions.

This may be regarded as a normal distribu3. Mean monthly deposits for summer half tion, as the winter months, including the two years, i.e., April to September, 1918 and 1919.

highest deposits, are the time when domestic 4. Mean monthly deposits for winter half

fires are in operation, while the lowest deposits years, i.e., October to March, 1918–19, and

occurring in May and September, are in the 1919-20.

summer months when fires are presumably not 5 and 6. Classification of stations accord- required. In Glasgow there is a second miniing to amounts of elements.

mum in December and February. Wind 7 and 8. Totals of classified stations for doubtless has a great influence on the quaneach element of pollution.

tity of deposit, high winds sweeping it away 9. Comparison of mean monthly deposit dur- from the vicinity of its origin and calm ing summer and winter.

weather favoring deposit near the source of 10. Average deposit of each element for each impurity. month for two London and four Glasgow sta- Of the research work, the chief problem has tions.

been accurate measurements of acidity in the Also six summaries and analyses.

air. Automatic filters have been devised, holdThe station showing the highest mean ing 24-hour discs and many records have been monthly deposit for the year is Southwark made of impurities in London air. It has been Park, London, with 15.35 metric tons per shown that there is a definite cycle in the dissquare kilometer, but it is said that probably tribution of the impurities during the 24 Newcastle or Rochdale, for which full year

hours. From midnight to 6 A.M. the air is results were not available, might have ex

practically clean of impurity, very little being ceeded this figure. The lowest value was 3.17

recorded except during fogs. At about 6 A.M., at Malvern.

when fires are lit, there is an increase in imThe following table gives the mean monthly purity continuing until 11. From 11 to 10 deposits as selected stations:

P.M. the quantity varies very little. At 10 it begins to diminish rapidly and has almost dis

appeared by midnight. SQUARE KILOMETER

The committee is considering the possibility Meteorological Office

8.43 of utilizing standard rain gages. For large deFinsbury Park ...

10.78 posits this might work, but for country places Ravenscourt Park


with small deposits the 20 cm. gage (8 inch Southwark Park


diameter) would not suffice since the area of Hesketh Park


this gage is practically 1/10 that of the standWoodvale Moss


ard deposit gage. One great objection to the 2 Abridged. Full table gives quantities of tar, use of the standard rain gage is the impossicarbonaceous matter, etc.

bility of estimating the quantity of tar and



sulphates present; and these indicate the reactions which take place in the organism origin of the deposit.

are due to enzymes. The mechanism of To investigate this matter, however, the enzyme reactions is therefore very closely committee had the water collected in the 8-in. connected with the mechanism of the living rain gage on the roof of the Meteorological cell. Many enzyme reactions, however, may Office analyzed for two or three months. Dur- be studied in vitro and are therefore amenable ing the month of November the small 8-in. to quantitative study. The present paper is gage collected 900 c.c. of water, the total de- an attempt to show that the peculiarities of posit was 0.445 gramme, the total soluble 0.34 a typical enzyme reaction, pepsin digestion, gramme, while in the standard deposit gage, may be explained by the accepted laws of the water collected was 783 liters, total deposit chemical reactions and that the apparent 1.962 grammes, total soluble 0.53 gramme. divergencies from these laws are due to the There was, therefore, a large excess of soluble fact that the enzyme as well as the protein matter in the water collected in the rain gage. with which it reacts exist in solution as equiThe same result was found in subsequent librium mixtures, consisting, in the case of months, and it was ascertained that the excess the protein of ionized and non-ionized protein, of soluble matter was due to metal dissolved and in the case of the pepsin of free and comfrom the rain gage.

bined pepsin. The influence of the various It was therefore useless to continue the ex- factors on the digestion are primarily due to periment unless the solution of the metal could changes in these equilibria. be prevented. In order to do this the rain

It is well known that enzyme reactions in gage was given a coating of Duroprene var

general have certain peculiarities which disnish, in the hope that this would prevent the

tinguish them from ordinary chemical resolution of the metal without any contamina

actions. These may be briefly stated tion of the water.

follows: The result of the analysis of a month's rain

1. The final amount of change caused by fall showed for the 8-in. rain gage a consider

the enzyme is independent of the amount of ably larger proportion of soluble and insol- enzyme present. uble matter per liter of water as compared

2. The rate of change may or may not be with the standard deposit gage, owing to the

proportional to the concentration of enzyme varnish yielding to the action of the rain present. water. It is therefore clear, if observations 3. The rate of change is proportional to the are to be taken with small gages these must be substrate concentration in dilute solution but constructed of something which will not dis

increases less rapidly than the substrate consolve in the water, and the use of the ordinary

centration in solution of higher concentration. copper rain gages is therefore inadmissible. 4. The amount of substrate decomposed in

the same time interval by varying enzyme ALEXANDER MCADIE

concentrations is not always proportional to

the concentration of enzyme but is often proSPECIAL ARTICLES

portional to the square root of this quantity THE MECHANISM OF AN ENZYME REACTION

(Schütz's rule). AS EXEMPLIFIED BY PEPSIN DIGESTION 5. The reaction proceeds most rapidly at

ONE of the most striking peculiarities of a certain definite hydrogen ion concentration. living matter is the fact that nearly all the It has been found in a study of pepsin 1 The experimental data on which this paper is

digestion that the above peculiarities may be based may be found in J. Gen. Physiol., 1918–19,

quantitatively accounted for on the basis of I., 607; 1919-20, II., 113, 465, 471, 595; 1920–21, the following mechanism. III., 211.

1. The protein reacts with the acid of the

[ocr errors]

solution to form an ionized protein salt. The action. It will be seen, however, that the amount of this salt formed is determined final equilibrium will depend to a slight exby the hydrogen ion concentration of the tent on the amount of enzyme present since solution according to the well-known laws some of the products of hydrolysis are comgoverning the reaction of an acid and a weak

bined with the enzyme. base.

2. Concentration of Enzyme.-If the en2. The pepsin is present in the solution, zyme solution is pure, the rate of hydrolysis, (a) as free, probably negatively charged other factors being constant, will be directly pepsin, and (6) in combination with the

proportional to the concentration of enzyme products of hydrolysis of the protein. These taken. If the enzyme solution contains two forms are in equilibrium with each other products of hydrolysis or other substances and their relative concentration depends on with which the enzyme is combined then the the amount of products of hydrolysis present rate of hydrolysis will increase more slowly in the solution as demanded by the law of than the concentration of enzyme solution mass action.

since the amount of free enzyme present be3. The reaction takes place between the comes relatively smaller the higher the conionized protein and the free pepsin.


3. Concentration of Protein. If the rate of EXPERIMENTAL EVIDENCE FOR THE ABOVE

hydrolysis of the protein is proportional to STATEMENTS

the concentration of ionized protein then the Loeba has shown by direct experiment that rate must increase more slowly than the total the protein exists in solution in an equi- protein concentration since the ionization of librium condition as stated under (1).

the protein salt is less in concentrated than Rekelharing and Ringers have shown that

in dilute solution. purified pepsin in solution is negatively 4. Schütz's Rule.-Arrheniust has pointed charged. It may be shown by direct experi

out that in an equilibrium system, such as ment that the addition of products of hydro- exists between free pepsin and the products of lysis decrease the activity of the enzyme and

hydrolysis, the concentration of one of the that the amount of the decrease in the

reacting molecules or ions becomes inversely activity can be predicted by the law of mass

proportional to the concentration of the action.

second as soon as the second is present in The validity of the third assumption may

large excess. That is, the amount of free best be tested by applying the proposed

pepsin present, after the first few minutes of mechanism to the explanation of the char

the reaction, is inversely proportional to the acteristic peculiarities of the reaction outlined under (1 to 5).

amount of products formed. It follows from

this that the amount of hydrolysis at any 1. Influence of Quantity of Enzyme on the Final Equilibrium.-Since the free enzyme

time is proportional to the square root of the and the products of hydrolysis are in equi

time elapsed, which is one form of Schütz's

rule. librium there will always be some active

5. The Influence of the Hydrogen Ion Con(free) enzyme present no matter how high the

centration.-It is clear that the more acid concentration of products becomes. The reaction will therefore proceed to approximately

is added to the protein the more protein salt

will be formed until all the protein is present the same point irrespective of the amount of enzyme present at the beginning of the re

in the form of protein-acid salt. This salt is

practically completely ionized in dilute solu2 Loeb, J., J. Gen. Physiol., 1918-19, I.; 1919-20,

tion as may be shown by direct measurement II.

3 Peckelharing, C. A., and Ringer, W. E., Z. 4 Arrhenius, S., “Quantitative Laws in Biolog. physiol. Chem., 1911, LXXV., 282.

ical Chemistry,” London, 1915, pp. 36-48.

[ocr errors]

this way.

of the anion concentration by means of con- from a quantitative standpoint each chemical centration cells. A further increase in the reaction is specific. It may be added that a amount of acid will now serve to decrease the very similar mechanism was proposed by concentration of protein ions by increasing the Stieglitz and his collaborators for the hydroconcentration of the common anion. The con- lysis of the imido esters by acid. centration of ionized protein will therefore It is, of course, impossible at present to pass through a maximum which should coin- apply these results directly to the activities cide with the maximum for the rate of of the living organism since conditions there digestion. If the ordinary theory of chemical are much more complex. It is probable, howkinetics, on the basis of the law of mass ever, that much of the apparent complexity action, be applied to the above system, it may is due to the fact that several processes, each be predicted that:

simple in itself, occur simultaneously and I. The optimum hydrogen ion concentra- thus lead to a complicated result. Dernby's5 tion for the digestion of the protein must experiments render it probable that the phecoincide with the hydrogen ion concentration nomenon of autolysis may be explained in at which the concentration of protein ions and therefore the conductivity due to the

JOHN H. NORTHROP protein is at a maximum.

ROCKEFELLER INSTITUTE FOR II. The limiting pH for the activity of MEDICAL RESEARCH pepsin on the alkaline side must depend on the isoelectric point of the protein, since this

KNIPP'S SINGING TUBE is the point at which the protein first begins My colleague, Dr. C. T. Knipp, when conto react with the acid.

structing a piece of apparatus, found that one III. The addition of a salt with the same of the parts—a glass tube intended for a anion as the acid to a solution already con

mercury trap-gave forth a musical sound taining the optimum amount of acid will under the heating action of a gas flame. Folhave the same depressing effect the lowing this clue he constructed various modidigestion as the addition of the same amount fications of the tube and described them with of anion in the form of acid.

the interesting results obtained. Inquiry has IV. The pepsin should combine with the been expressed concerning the explanation of protein only when the latter is ionized, i.e., its action. It occurred to the writer that this pepsin should behave the same

as the in

explanation might be found in the theory adorganic anions studied by Loeb.

vanced for similar cases where sounds are These predictions have been tested quanti- maintained by heat.? tatively and found to be fulfilled. It has also

Fig. 1 pictures one type of the tubes tested. been found by direct experiment that neither It is a resonator with a loop at A and a node the influence of the acidity on the destruction at N, so that the distance ABCN constitutes of the enzyme, nor the viscosity of the protein approximately one fourth of the wave-length

, solution can account for the influence of the

of the sound given out by the tube when hydrogen ion concentration on the rate of

operating. The air surges back and forth at digestion.

A with the greatest velocity and displacement. It will be seen that from this point of view

From this point the to and fro motion of the pepsin digestion is a chemical reaction in

5 Dernby, K, G., Biochem. Z., 1917, LXXXI., which the pepsin as well as the protein takes part. It is therefore not a catalytic reaction

1 Phys. Rev., Vol. 15, p. 155, 1920; and other at all in the classical sense. The specificity

publications. of the reaction is therefore probably governed 2 Rayleigh, “Theory of Sound,” Sec. 322. Barby the same conditions that determine the ton, “Text-Book of Sound,” Sec. 265–277. specificity of any chemical reaction, since 8 Phys. Rev., Vol. 15, p. 336, 1920.



[ocr errors]
« iepriekšējāTurpināt »