X hits on this document

16 views

0 shares

0 downloads

0 comments

4 / 8

686

REACTION

OF

NINHYDRIN

WITH

DIPEPTIDES

Factors Which methyl Cellosolve

A$ect Reactivity had a pronounced

of Dipeptides-The effect on the molar

concentration of color yields of the

diastereoisomers reaction period

with ninhydrin are expressed in

(Fig. 3). The results for a terms of leucine units, since the

12 minute color yield

for this amino color yield of

acid was only slightly

n-Leu-L-Tyr

increased

affected linearly

under these conditions.

The

with

increasing

concentration

of its

the organic solvent6 maximal value at

and approached approximately

that of L-Leu-L-Tyr, 33 volume per cent.

which reached These data ac-

count

for

the

earlier

observation

(Fig.

1)

that

only

the

reaction rate of

D-Leu-L-Tyr with water.

was appreciably

affected

by dilution

of the reaction

mixture

I

f

I

I

1

I

OO

“OLEE

P2EoRCE3NoT ME%

60 EL.OSOL”E

70

FIG. 3. Effect

minute peptide

reaction or leucine,

of methyl

Cellosolve

period.

Each reaction

112 pmoles

of ninhydrin,

on the mixture

color

(2.0

3.5 pmoles

yields

of diastereoisomers;

ml.)

contained

0.1

of SnClp,

and

0.1

pmole M citrate

12 of

buffer

(pH

5.0).

Somewhat greater reaction rates were obtained when the SnClz-nm-

hydrin Nearly

reagent was replaced by equal rates for L-Leu-L-Tyr

the hydrindantin-ninhydrin

reagent.

and D-Leu-L-Tyr

were observed with

the

latter

reagent and high

methyl

per

cent).

The importance

of this

fact that the reaction as in Fig. 3 with the

Cellosolve concentration

(65 volume

organic solvent was illustrated

by the

rate for D-Leu-L-Tyr was decreasedmore than 2-fold,

SnC&ninhydrin

reagent,

when

the

concentration

of

the methyl Cellosolve was decreasedfrom 65 to 25 volume per cent.

the other

hand, a 3-fold

no effect.

These data

decreasein the concentration of hydrindantin rule out stannous and stannic ions and the

On had con-

by

the

limited

solubility

of hydrindantin

in water,

in subsequent

the

text),

at

concentrations

of solvent

>25

per cent,

hydrindantin

e Although

factor.

the

data

for very

low

concentrations

of organic

solvent

may

be affected

experiments

(see

was not

a limiting

Downloaded from http://www.jbc.org/ by guest on February 9, 2015

Document info
Document views16
Page views16
Page last viewedFri Oct 28 10:26:24 UTC 2016
Pages8
Paragraphs1219
Words2631

Comments