j. biol. chem. 1952 copeland 331 41

STUDIES IN SERUM ELECTROLYTES

XVIII. THE MAGNESIUM-BINDING PROPERTY OF THE SERUM PROTEINS*

BY BRADLEY E. COPELANDt AND F. WILLIAM SUNDERMAN

(From the Division of Metabolic Research, Department of Medicine, Jefferson Medical College, Philadelphia, Pennsylvania)

(Received for publication, February 13, 1952)

Evidence has accumulated from numerous sources that solutions containing protein and divalent cations of the alkaline earth series do not follow the laws of electrolyte distribution (i.e. Donnan equilibrium) with respect to ion transport or semipermeable membrane systems. Various investigators have explained these discrepancies by the formation of a complex cation proteinate. Thus, Northrop and Kunitz (20) demonstrated by measurement of ion transfer that, in a mixture of gelatin (10 per cent.) and zinc chloride (0.10 M), 61 per cent of the zinc was bound to the gelatin. These workers also showed that the ratio of the concentrations of Ca, Mg, K, and Zn inside and outside of a gelatin block did not agree with rat.ios calculated according to the Donnan theory and that these discrepancies could be accounted for by the presence of a combination of the gelatin with the cations.

Greenberg and Schmidt (11) showed by their work on transport numbers in solutions of casein and cations of the alkaline earth group (magnesium, strontium, and barium) that part of the cat.ion was held by the casein in the form of a complex ion. For magnesium and calcium they calculated the amounts that were bound per gm. of casein and noted that the maximum amount of alkaline earth held by 1 gm. of casein tended to reach a maximum value which was constant, and independent of the divalent cation used. Thus, it was postulated that when maximum amounts of alkali were used the complex ion, casein-alkaline earth, had a definite composi- t.ion.

Of the cationogens present in human serum t.he divalent ones, calcium and magnesium, are not freely diffusible through a semipermeable membrane (25, 27), in contrast to the monovalent cations which are freely diffusible (29, 24). Of the two divalent cationogens, the base-binding property of calcium has been more intensively studied than magnesium.

McLean and Hastings (17) demonstrated that most of the calcium which passed t.hrough the semipermeable membrane was in the ionized form.

* Aided in part hy a graut from the Office of Naval Research. t Present address, New England Deaconness Hospital, Boston, Massachusetts.

331

by guest on January 21, 2015http://w

ww

.jbc.org/D

ownloaded from

by guest on January 21, 2015

http://ww

w.jbc.org/

Dow

nloaded from


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/http://www.jbc.org/http://www.jbc.org/

332 SERUM ELECTROLYTES. XVIII

Their datn were derived from experiments in which the frog heart was used as a biological indicator of ionized calcium. This method is based upon the observations that the frog heart is sensitive to changes in concentration of calcium ion and that solutions containing equal concentrations of calcium ion induce equal responses in the heart. The reaction of the frog heart appears to be specific for the calcium ion. Complex calcium ions and non-ionized calcium compounds fail to show any effect upon the frog heart preparation.

Serum protein, being amphoteric, is dissociated in the anion form at the pH of human serum. Calculations by McLean and Hastings (17) showed that in the calcium-proteinate complex the protein units acted as divalent anions according to the formula

1 ii C-O-H+ OH- c-o

/ / / \ (1) R, . + Ca, + R, ,Cas2HrO

C-O-H+ OH- c-o

II II 0 0

This was based on the observation that, whereas calculations assuming each protein unit to be divalent gave a constant dissociation value when applied to the mass law equation, the calculations assuming each protein unit to be monovalent did not give a constant value when applied to the mass law equation. A dissociation constant for calcium and protein (pK CaProt)* was calculated by these workers (17) from the mass law relationship as given in Equation 2.

(2) (Cs++)(Prot-)

(CaProt) = Kca~rot

It was assumed that

(3) (Total Ca) - (Ca ion) = (CaProt)

(4) (Total protein) - (CaProt) = (Prot-)

This relationship was confirmed by Masket et al. (16) by measuring, in solutions containing calcium and protein, the concentrations of calcium and protein at selected levels after ultracentrifugation. When these values for calcium and protein were plotted, it was shown that the concentration of ionized calcium could be calculated by extrapolating the curve of the plotted results to zero gm. of protein. Thus, by physical means the re-

1 Prot = proteinate.


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/

B. E. COPELAND AND F. W. SUNDERMAN 333

lationship of calcium and protein in the serum wm shown to hold in accordance with the law of mass action.

It would seem probable that the magnesium of the serum would follow the same pattern as the calcium of the serum. Greene and Power (12) reported that in a protein-containing solution the ratio of diffusible to nondiffusible magnesium was approximately equal to the ratio of diffusible to non-diffusible calcium. The per cent of total serum magnesium which diffuses through a semipermeable membrane has been measured by several investigators. Average normal values reported for diffusible magnesium range from 57 per cent (6) to 84 per cent (26), and results within these limits have also been reported (4, 35, 27, 15).

The present studies were undertaken in an effort to demonstrate the partition of magnesium into diffusible and non-diffusible moieties in normal human serum, and also to determine the magnesium-binding power of the serum protein fractions, albumin and globulin, in normal human serum.

Methods

Diffusible magnesium was determined by measuring the concentration of magnesium in a protein-free ultrafiltrate of serum.2 The magnesium bound to globulin was calculated as the difference bet,ween the concentration of magnesium in the original serum and the concentration of magnesium in the same serum after precipitation of the globulins with methanol. The remaining magnesium fraction less the diffusible magnesium was considered to be bound to albumin. It w&s assumed that the magnesium remained bound to the globulin during the precipitation procedure. At present, there is no evidence bearing upon this assumption.

Samples of blood were withdrawn under oil without stasis, subsequent to the withdrawal of 500 ml. of blood for transfusion purposes, from healthy, fasting, adult donors. It has been shown that the concentrations of serum protein and total base undergo no significant change immediately after withdrawal of 500 ml. of whole blood.3

Protein-free filtrates were prepared by suction filtration through 23/32 inch Nojax casing (Visking Corporation, Chicago) with a Greenberg- Gunther apparatus &s modified by Rawson and Sunderman (23).

The concentrations of magnesium in the whole serum, globulin-free filtrate, and ultrafiltrate of serum were measured by the Fiske and Subba- row (8) modification of the Briggs (5) method. After the removal of calcium as calcium oxalate, the magnesium was precipitated from the supernatant serum plus diluent and washings as MghHdPOd.6H20. The

1 There is as yet no method for ionized magnesium (Mg++) comparable to the frog heart method for ionized calcium (Ca++).

8 Unpublished work of F. William Sunderman and B. E. Copeland (1949).


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/


phosphate was then determined as phosphomolybdate with 1,2,4-amino- naphtholsulfonic acid as the reducing agent. Measurements were made with a Bausch and Lomb calorimeter of the Duboscq type, fitted with a Wratten No. 24 filter and an attachable lamp.

An aqueous magnesium standard prepared from MgSOh in a concentration of 2.00 m.eq. per liter was quantitatively recovered with an error of fl per cent by this mct.hod. A faint blue color was observed in the reagent blank analyses which could not be read in the calorimeter unless a dilute phosphate standard was prepared. Inst,ead of making measure- mcnts directly on the blank, a constant amount of phosphate was added to t.he blank just before color development, and measurements were made on this solution. This procedure brings the color to be read within the optimum zone for reading in the visual calorimeter. The blank values for the total serum and ult,rafiltrate of serum ranged from 0.0 to 0.2 m.eq. per liter; for the globulin-free serum, 0.0 to 0.4 m.eq. per liter.

Protein nitrogen, non-protein nitrogen, and albumin nitrogen were measured by the modification of the Parnas-Wagner-Kjeldahl method described by Hiller et al. (13), which was found to give in known solutions recoveries of 100.0 f 0.1 per cent of the theoretical value of the nitrogen standard. The serum globulin was precipitated by the method of Pillemer and Hutchinson (22) with methanol at 0 and pH 6.8. This method has been shown to approximate closely the albumin-globulin separation by electro- phoresis met,hods.

The specific gravit,y of the serum was measured at 20 with a 5 ml. pyknometer. In a few cases the calculations for conversion to units per kilo of water were made from the formula Hz0 gm. per 100 ml. of serum = 99 - 0.08 (protein) (32).

Magnesium and protein have been expressed in terms of serum water. The relationships were calculated in accordance with the equation previ- ously described by Sunderman (28).

All measurements were made in duplicate. Duplicate determinations checked within approximately f4 per cent.

Results

Table I shows the raw and calculated data of seventeen normal human sera from which the pK magnesium proteinate was calculated. Two assumptions have been made: (a) that diffusible magnesium is in the ionized form; and (b) that, for the purpose of expressing protein in terms of milliequivalents per liter of serum, t.he pH of the serum was 7.4.

These are the same assumptions mad{: by McLean and Hastings (17) in their work on the dissociation constant. of calcium proteinate. The average albumin-globulin ratio of our protein measurements was 1.67.


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/


me mean pKhlsProt was found to be 1.77, s.d. f 0.15. The magnesium ion (Mg*) concentrations were calculated by the formula derived by McLean and Hastings (17) for the calculation of calcium ion concentration, with total protein and, in their case, total calcium and KCaProt values. The values for (Prot-) and (MgProt) may be obtained from Equations 5 and 6, respectively.

(5) (MgProt) = (total Mg) - (Mg++)

(3) (Rot-) = (total protein) - (MgProt)

These values are then substituted in the first approximation of the mass law equation (No. 7)

(7) (Mg++)(Prot)

(MgProt) = Kmn~rot

and the resulting quadratic equation solved for (MC), as in Equation 8.

03) (Mg++) =

(total Mg) - (total P) - K -I- 44K(total Mg) + ((total P) + K - (total Mg)) 2

When all the values are expressed as milliequivalents per kilo of HSO, the average value of KhlgProt in Equation 8 is equal to 33.766.

For the series of seventeen normal sera (Table I) the mean difference between the calculated and observed Mg++ values was 0.12 m.eq. of Mg++ per kilo of HzO, s.d. ~0.067.

Complete analyses of six normal sera were available for the calculations of the magnesium-binding power of albumin and globulin. Table II gives the raw data, calculated magnesium and protein partitions, and the magnesium-binding power of albumin and globulin. The binding power per gm. of albumin was 0.013 m.eq. of Mg (s.d. ~1~0.004) and the binding power per gm. of globulin was 0.008 m.eq. of Mg (s.d. ~tO.003).

DISCUSSION

From a large series of serum samples Watchorn and McCance (34, 35) suggested that there was a tendency for the magnesium concentration in the ultrafiltrate to be inversely proportional to the total serum protein. They demonstrated that as the concentration of total serum protein in- creased the ratio of diffusible magnesium to total magnesium fell. Thus, with serum proteins below 6 gm. per 100 ml., the ratio was 0.797, with proteins between 6 and 7, the ratio was 0.752, and with proteins of 7 and over the ratio was 0.718.

Watchorn and McCanccs values for serum magnesium, ultrafiltrate

P = protein in Equation 8.


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/


-!-

-

-

-

-


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/

82000~ O

WO

OT

18000 82100

ps =I= xm

od Bu!p!q

U8aW

9ZI 191 19-1 80'1 IO'

I 68'0

298 89P IW

809 8Zli 8ZP

_--- 1 q

&ZO LIO 800 920 LZO 98.0 __ 2 %.

s:o El

. - - -

-

- -

982 ix2 892 118 908 LLL

-I-

-

- i

- 829 Z69 P69 Po8 608 898

190 ZEO

Z90 SL.0 990 16'0

PLO

69'0 09'0 10'1 28'0 9Z'I

OO

Z O

OZ

II'Z 6O'Z B3*1 SI'Z

098 L.89

LZP Z'S9

9'IP P's9

ILP Z'9L

P'6P 19L

9'8P L'B.!

9Zz'I 091 09'1 u)I 001 880 t? .!E P q5

88'1 88'1 86'1 96'1 IL'1 OO'Z

9800'0 9PIO'O

5 ILal'O

1LOO'0 2

ZEOO'O 81100

8 L64lO'O

6VIO'O 8600'0

8010'0 po10'0

PLIO'O

ZszO'I +09ZO'I l 09ZO'I

2820'1 2820'1 BZO'I

- -.

Y m ? 2; < ?

L9'1 ZL'I 16'1 99.1 99'1 89'1

z$ O

e 6 6

- w+w

umunH

gg~gg =

x JO

arqm

aPtxa~~ aq~,

8 uoymb3

01 Bu!p~ooas pa~qnqs3

I(

'91'01 'P'S

'LL'I =

-~)Id a%

sraay $

~UO!$~J~U~~UO

~ J8lO

JO

SUIlaJ U

! dnm

x 1

02~ Jo o[q

dad sgua[8ynbaqly =

(poo[) ~aq![ Jad s)uaIm

!nbag~~ uopi~a~uoa

a~uqgvqn 4

OH

Jo 01q Jad s~uaIm

!nba!l~!ru u! %

oJd = @

H 30 01q

Jad mfd u! u!alold

(zf+yO) uoym

ba uo!a~a~uo~

*(68'P -

Hd)(h !IVIfd)

8PO +

(919 -

Hd)(N !nW

) 8.4.0 =

&I : (I&)

Y ?J


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/

338 SERUM ELEClROLYTES. XVIII

magnesium, and serum protein of normal and abnormal sera (35) were converted to a serum water basis. Uy using the pK,,,,,, derived from the normal sera in this study, the ionized (Mg++) concentration was calculated according to Equation 8 and a comparison made of the measured and calculated values for ionized magnesium. In their eight normal subjects the mean deviation of calculated ionized (Mg++) concentrations from the measured ultrafiltrate magnesium was 0.09 m.eq. per kilo of HSO. Analy- ses of forty-three pathologic sera (Watchorn and McCance (35)) having a range of t,otal serum magnesium from 1.57 to 10.34 mg. per 100 ml. of serum and a range of total serum protein concentration from 4.2 to 8.5 gm. per 100 ml. of serum were also used in calculating t,he concentration of ionized magnesium according to Equation 8. The deviations of the calculated values from the observed values are shown in Table III.

The six sera with deviation of calculated Mg++ from the measured Mg*

TABLE III

Analysis of Data of Watchorn and McCance (S4, 36)

Deviation of calculated Mg++ from observed No. of samples

m.cq. per kg. Eta

0.05 or less 0.0&0.10

0.10.15

O.lso.2u

0.2J30.25

0.25 and over

14 13

7 6 5 6

of more than 0.25 m.eq. per kilo of Hz0 were from patients with nephritis or other renal complications.

Statistical analysis was made of the combined 68 pairs of measurements reported in this study and thi: studies of Watchorn and McCance. The correlation coefficient of the calculated values of Mg++ to the observed values for Mg++ was 0.980, with confidence limits at t.he 95 per cent level of 0.967 to 0.989. The confidence limits were established for the corrcla- tion coefficient by use of the Z transformation (Fisher (7)). Thus, the correlation coefficient of 0.980 obtained from the present data on magnesium is in agreement with the correlation coefficient of 0.981 obt.ained for calcium in the study of McLean and Hastings (17).

A regression line (y = a + bx) was prepared to test the departure of the calculated values from the observed values. The observed regression line was y = 0.996x - 0.023.

A test of statistical significance indicates that a (-0.023) is not sig- nificantly different from 0, and that b (0.996) does not. differ from 1 at the 1 per cent level of significance. It is unlikely, therefore, that there is


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/

TABL

E IV

Sum

mar

y of

M

ethod

s an

d Re

sults

of

M

easu

rem

ents

of

Lllr

ajiltr

ate

Mag

nesiu

m

Conc

entra

tion

in

Norm

al Se

ra

Inve

stig

ator

Star

y an

d W

inter

nit

z (2

7)

Wat

chor

n an

d M

cCan

ce

(35)

So

ffer

et

al.

(26)

Lavie

tes

and

Dim

(15)

Biss

ell

(4)

Cope

an

d W

olf

(6

This

pa

per,

Cope

- lan

d an

d Su

n-

derm

an

I- 1 ) -

Subje

cts

Metho

d of

Mg

analy

sis

Metho

d of

ultra

filtra

tion

Hum

an

4M.,4

F.

14

Com

pens

ation

di

alys

is

Gree

nber

g-Gu

nther

(1

0)

1%

mm

. Hg

su

ctio

n No

. 60

0 ce

lloph

ane,

30

lb

s.

per

sq.

in.

N

4 M

., 13

F.

, 15

-B

yrs.

17

Wat

chor

n (3

3);

Bell-D

oisy

(1);

Brim

s (5

) Br

iggs

(5)

PO,;

Kuttn

er-

Lich

tens

tein

(1

4)

moly

b-

date

-SnC

L As

hing

, pp

t. LM

gNH,

POd;

Bene

dict

-The

is (2

) ino

r- ga

nic

P Br

iggs

(5)

; Ts

chop

p-

Tsch

opp

(30)

Pe

ters

-Van

Sl

yke

(21)

;

Bere

nblum

-Cha

in (3

) Sn

Cle

Brigg

s (5

) NH

dMgP

O,;

Fisk

e-Su

bbar

ow

(8)

1,2,

4 am

inon

apht

holsu

lfoni

c ac

id

Cello

phan

e,

anae

robic

, 23

1.

57

cm.

Hg

(1.31

-1.35

)

9M.,9

F.

No.

450

cello

phan

e,

Lavi-

et

es-D

ine

(15)

, 23

cm

. Hg

No

. 30

9 ce

lloph

ane,

2.

5 at-

m

osph

eres

Gree

nber

g-Gu

nther

(lo

), 1.

77

150

mm

. Hg

su

ctio

n (1

.46-1

.98)

- -

Tota

l M

g

m.cp

. pe

r 1.

2.04

(2

.02-2

.05)

(X2.

27)

(Z-2

.21)

1.64

(1

.44-2

.02)

-

1

-_ -

fJltra

6ltra

te

Mg

m.e

q. p

er 1.

1.48

(1

.32-1

.56)

1.77

(1

.42-2

.04)

(El

.48)

1.36

(1

.03-1

.46)

1.03

(0

.41-

l .7

3)

(E&3

)

Per

cent

diffus

ible

Mg

td

72

m

8 m

(z-76

) 5


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/


included in the concentration of Mg++ any appreciable quantity of magnesium in a form other than ionized magnesium.

The fact that the dissociation constant for magnesium proteinate (~JLmrot ) holds for serum magnesium values as high as 8.52 m.eq. per kilo of H?O is evidence in favor of the assumption that throughout a wide range of magnesium and protein values the mass law relationship operates.

According to the equation for neuromuscular irritability,

[Na+l[K+l Irritsbility = [~pfl[~a++j[~+l

both magnesium and calcium have a depressant action as their ion concentration increases. The apparent lack of depressant action of calcium at high serum concentrations may be due to the formation of a calcium phosphate complex (9, IS), whereas the magnesium concentration at anes- thetic levels (4.1 to 16.4 m.eq. per liter of serum for the dog (19)) still has not exceeded the solubility levels of its possible serum salts and con- tinues to dissociate according to the mass law relationship. Greenberg (9) has stated that increasing the magnesium concentration of a protein- containing solution did not affect the ultrafiltrability of the magnesium.

There has been some difference in the reported measurements of concentration of ultrafiltrate magnesium, and the per cent of the total magnesium concentration which this constitutes. Table IV gives a summary of the methods employed and results obtained by various investigators for normal human subjects.

SUMMARY

1. Magnesium proteinate in the serum acts aa a dissociated salt, according to the mass law relationship.

2. A dissociation constant for this relationship was calculated from measurements made upon seventeen normal sera. This constant, pKmProt, was found to be 1.77, s.d. f0.15.

3. This constant was used to calculate Mg++ of the seventeen normal sera in this study as well as eight normal and forty-three abnormal sera from a study of Watchorn and McCance. The coefficient for the correlation of the calculated magnesium ion values to the obserued magnesium ion concentration was 0.980. Therefore, it is apparent that the concentration of magnesium ion in serum may be calculated from the concentrations of total magnesium and total protein of serum with a high degree of accuracy.

4. From our data, it would appear that the diffusible magnesium in serum is practically all ionizable. However, it is possible that there may be present a small percentage of diffusible magnesium that is non-ionized.

5. The relationship between magnesium and protein in serum has been shown to hold over a wide range of their concentrations.


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/


6. The magnesium-binding power of the serum protein fractions was calculated from measurement5 of six normal sera. The magnesium-binding power of albumin was found to be 0.0128 (s.d. &0.004) m.eq. of Mg per gm. of albumin. The magnesium-binding power of the globulin was found to be 0.0081 (s.d. ~0.0028) m.eq. of Mg per gm. of globulin.

We wish to acknowledge with appreciation the technical assistance of Mrs. Jane Perna.

BIBLIOGRAPHY

1. Bell, R. D., and Doisy, E. A., J. BioZ. Chem., 44, 55 (1920). 2. Benedict, S. R., and Theis, R. C., J. BioZ. Chem., 61, 63 (1924). 3. Berenblum, I., and Chain, E., B&hem. J., 32, 286 (1936). 4. Bissell, G. W., Am. J. Med. SC., 210, 195 (1945). 5. Briggs, A. P., J. BioZ. Chem., 62, 349 (1922). 6. Cope, C. L., and Wolf, By., Biochem. J., 56, 413 (1942). 7. Fisher, R. A., Statistical methods for research workers, London, 10th edition,

197-201 (1946). 8. Fiske, C. H., and Subbarow, Y., J. BioZ. Ckem., 66, 375 (1925). 9. Greenberg, D. M., Proc. Sot. Exp. Biol. and Med., 30, 1005 (1932-33).

10. Greenberg, D. M., and Gunther, IA., J. BioZ. Chem., 86, 491 (1929-39). 11. Greenberg, D. M., and Schmidt, C. L. A., J. Gen. PhySioZ., 8, 271 (1925). 12. Greene, C. H., and Power, M. H., J. BioZ. Chem., 91, 183 (1931). 13. Hiller, A., Plazin, J., and Van Slyke, D. D., J. BioZ. Chem., 176, 1401 (1946). 14. Kuttner, T., and Lichtenstein, L., J. BioZ. CAem., 86, 671 (1930). 15. Lavietes, P. H., and Dine, R., J. Clin. Invest., 21, 781 (1942). 16. Masket, A. V., Chanutin, A., and Ludewig, S., J. Biol. Chem., 14. 763 (1942). 17. McLean, F. C., and Hastings, A. B., J. BioZ,Chem., 109, 2% (1935). 18. Moore, N. S., and Van Slyke, D. D., J. CZin. Invest., 8, 337 (1930). 19. Neuwirth, I., and Wallace, G. B., J. Phurmacol. and Ezp. Therap., 36, 171 (1929). 20. Northrop, J. H., and Kunitz, M., J. Gen. Physiol., 7, 25 (1925). 21. Peters, J. P., and Van Slyke, D. D., Quantitative clinical chemistry; Methods,

Baltimore (1932). 22. Pillemer, L., and Hutchinson, M. C., J. BioZ. Chem., 168, 299 (1945). 23. Rawson, A. J., and Sunderman, F. W., J. Clin. Invest., 27, 82 (1948). 24. Richter-Quittner, M., Compt. rend. Sot. biol., 91, 593 (1924). 25. Rona, P., and Takshashi, D., B&hem. Z., 31, 336 (1911). 26. Soffer, L. J., Cohn, C., Grossman, E. B., Jacobs, M., and Sobotka, H., J. Clin.

Invest., 20, 429 (1941). 27. Stary, Z., and Winternits, R., ZI physiol. C&m., 199, 107 (1929). 23. Sunderman, F. W., J. BioZ. Chem., 113, 111 (1936). 29. Tschimber, H., and Tschimber, C., Compt. rend. Sot. biol., 91,592 (1924). 30. Tschopp, E., and Tschopp, E., Helu. chim. acta, 16,793 (1932). 31. Van Slyke, D. D., Hastings, A. B., Hiller, A., and Sendroy, J., Jr., J. BioZ. Chem.,

79, 769 (1923). 32. Van Slyke, D. D., Wu, H., and McLean, F. C., J. BioZ. Chem., 66,766 (1923). 33. Watchorn, E., Brit. J. Ezp. Path., 7, 120 (1926). 34. Watchorn, E., and McCance, R. A., Quart. J. Med., 24,371 (1930-31). 35. Watchorn, E., and McCance, R. A., Quart. J. Med., 26, 54 (1932).


ww

.jbc.org/D

ownloaded from

http://www.jbc.org/

CORRECTION

In Equation 8, page 335, Vol. 197, NO. 1, July, 1952, the last member under the radical sign should be raised to the second power:

4.. . ((total P) + K - (total Mg))z

SundermanBradley E. Copeland and F. William PROPERTY OF THE SERUM PROTEINSXVIII. THE MAGNESIUM-BINDING STUDIES IN SERUM ELECTROLYTES:ARTICLE:

1952, 197:331-341.J. Biol. Chem.

http://www.jbc.org/content/197/1/331.citation

Access the most updated version of this article at

.Sites

JBC AffinityClassics on similar topics on the Find articles, minireviews, Reflections and

Alerts:

When a correction for this article is posted

When this article is cited

alerts to choose from all of JBC's e-mailClick here

tml#ref-list-1

http://www.jbc.org/content/197/1/331.citation.full.haccessed free atThis article cites 0 references, 0 of which can be


ww

.jbc.org/D

ownloaded from

http://affinity.jbc.org/http://www.jbc.org/content/197/1/331.citationhttp://affinity.jbc.orghttp://affinity.jbc.orghttp://www.jbc.org/cgi/alerts?alertType=citedby&addAlert=cited_by&cited_by_criteria_resid=jbc;197/1/331&saveAlert=no&return-type=article&return_url=http://www.jbc.org/content/197/1/331.citationhttp://www.jbc.org/cgi/alerts?alertType=correction&addAlert=correction&correction_criteria_value=197/1/331&saveAlert=no&return-type=article&return_url=http://www.jbc.org/content/197/1/331.citationhttp://www.jbc.org/cgi/alerts/etochttp://www.jbc.org/content/197/1/331.citation.full.html#ref-list-1http://www.jbc.org/content/197/1/331.citation.full.html#ref-list-1http://www.jbc.org/

j. biol. chem. 1952 copeland 331 41

Documents

complex ion

complex calcium ions

ion transport

caseinalkaline earth

divalent cations

solutions of casein

nonionized calcium compounds

alkaline earth group