Vibrational Raman optical activity of biopolymers

Journal of

MOLECULAR STRUCTURE Journal

Vibrational

of Molecular

Structure

Raman

349 (1995)

397-400

optical

activity

of

Biopolymers L. D. Barron, Chemistry

L. Hecht,

Department,

Vibrational solution.

about

Typical

are

and D,O

and G. Wilson

Glasgow

activity

G12 8QQ,

measurements

the structure

results

in HZ0

A. F. Bell

The University,

Raman optical

new information albumin

S. J. Ford,

can now

and conformation

exemplified

solution,

here

and for

United

Kingdom

provide

a wealth

of biopolymers

for

proteins

polysaccharides

by

of

in aqueous

bovine

serum

by laminarin.

1.INTRODUCTION Raman optical vibrational

activity

Raman

polarized sensitivity in

the level 3-6

this

directly

make

parent

AND

Vibrations backbone

band

incisive only

mode

contributions

to

band patterns patterns

and

CCD

which

detection

spectra

new

probe

of of

few

local

sample

the

the

which

and

left

have

based

on

enhanced

the

biological

molecules

biopolymer

solution

vibrational skeletal

coordinates

chirality

associated

ROA

intensity,

are usually

much

simpler

carry

information

of

circularly

instrumentation

ROA

those

which

in right

in

intensity

most thereby

than

about

the

absolute

of

PROTEINS the

peptide

spectrum:

C,-N in

similarities

all

four

with

the

signatures

there

appear

great

potential

to

backbone

the backbone

stretch

at mu1230-1350 cm-‘,

clear

and

in the

and conformation.

2. PEPTIDES

the Raman

filters

an

difference

molecules

advances

to provide

because

significant

Raman

is

normal

characteristic

configuration

appear

is

a complicated

generating

notch

ROA

a small

chiral

Recent

necessary

solution.

conformation:

measures

from

light. lp2

holographic

to

aqueous

within

scattering

incident

backscattering,

(ROA)

region regions extended

be

prominent

value

in

spectra

from

Science

I region most of

protein

of tertiary

at

ROA

peptide

from

main

ru 870-950 amide

cm-‘.

regions

of

cm-‘,

the

spectra,3’4

region

III

Signals

usually

which

show

oligomers.

’ In addition to such as a-helix and P-sheet,

loops

structure

All rights reserved

four

the extended

structures

signatures B.V.

with

region

at N 1645-1680

alanyl

secondary

in the study

0022-2860/95/$09.50 0 1995 Elsevier SSDI 0022-2860(95)08793-l

stretch

at N 1020-1150 cm-‘,

and the amide ROA

are associated

C,-C

and

turns3’4

and dynamics

which

have

of proteins.

398

1

BSA (Hz01

1.4x104 >

I

,

I

,

,

,

,

,

,

,

,

,

CT:

,

I,,

1

( , , , , ,

BSA (D,O)

\

RO

1.5x10

4

CIIY

,,,,,,,,,,,),,,,,

500

Figure

1. Backscattered

serum

albumin

,

650

800

Raman

in hydrated

(IR

950

11001250

+ IL)

and deuterated

and buffer

1400

ROA (pH

(IR

I

I

I

15501 -

= 5.4).

r

IL)

spectra

of

bovine

399

D-laminaribiose

ROA

[

7.5x103 ,

I

I

V

I,,

I,

,

(I,

(

,

,

,

I,,

,

cm,

ROA

V

1.6~10~

Figure

2. Backscattered

of laminarin

Raman and ROA

in tris buffer

(pH

= 7.5).

spectra

of

cm -’

D-laminaribiose

in H,O,

and

Comparison extended by

of

amide

N-D

removes

to dominate the

ROA the

chiral

provides

a good

structure

made

the large

example

striking cm-’

loops,

of

adjacent

assignment

would

change

and

of H,O

vibrations:

in

particular

skeletal cm-’

which

a- or

spectra

information Figure of

D-laminaribiose. glycosidic the

reflect

of

strong 1245

can

at N 1125 and 900 carbonyl

remaining account

ROA

in the The

band

at m

confirms of

assigned and

The

of

measured.

outside

I couplet

by

(BSAI

NH protons was

be

cm-‘.

the

which

features

mostly

on

positive

cm-’

amide

in aqueous

their

the to

the

positive

amide a-helix

positive

ROA

band

deformations.

of

nature

OH of

solution

secondary

structure

spectrum

of

ROA

with

that

ROA

spectra

IOSO

and

contribute from

triple

to

helical

the pattern

the

normal

the dimer

of

to

structures.

hydrogen

a 8(1-3) below

where

CO

modes,

the

the

of

also

the

exocyclic

appears

linked

corresponding

are similar cm-‘,

There

about

to be

in polysaccharides.

the

IISO

information

conformation

link.6

laminarin,

of

give

the

substituents,

the glycosidic

the

on going

formation

might

*

ROA

extended

N

oxygen

are reversed

the

at

with

the

N-H

albumin

rigid

ROA

The

of

deformations

serum

of

the

solution

in a-helix

pattern

The two

between

of

band D,O

C,-H

and

Most

when

useful.

generated

a-helical

double

bridges.

positively-biased

bands

together

D-glucose,

region

the

and the

about

are

exchanged

in

just

Bovine

is highly

3 The backbone

carbohydrates

2 shows

leaving

very

replacement

the ROA is now

which

disulphide

originate

the

groups,

BSA

are

because

a-carbon.s

of

ROA

solution

AND POLYSACCHARIDES

of

l3-anomer,

CHBOH

Il.

persist

stretch

might

3. CARBOHYDRATES ROA

the

have

structures.

in

at w 400

so that

many

negative

III region backbone

of

not

D,O

informative

is the disappearance

the

to loop

and

deformations

here

(Figure

up of

number

most

N-H

modes

environment

structures

1340

in Hz0

is particularly

crucial

the normal

local

a-helix

spectra

III region

polymer

The

bonding

disaccharide

N IO.50 cm-‘. stretches signs

which

large

polysaccharide

l3(1-3)

But in the

involving

of

the

ROA

we believe

differences

above

CH,OH

groups

between

the signals

is due 1200

to

cm-’

along

the

helix. REFERENCES 1. L.

D.

Molecular

Barron,

University

Press,

2. L. D. Barron

Light

Cambridge,

and L. Hecht,

(K. Nakanishi,

N. Berova

and

Scattering

and

Optical

Activity,

Cambridge

1982. in Circular R. W.

Dichroism:

Woody,

Principles

eds.),

VCH

and

Applications

Publishers,

New

York,

1994, p. 179. 3. Z. Q. Wen, 4. Z. Q. Wen,

L. Hecht

and L. D. Barron,

J. Am. Chem.

L. Hecht

and L. D. Barron,

Protein

S. S. J. Ford,

Z. Q. Wen,

6. A. F. Bell,

L. Hecht

L. Hecht

Science,

and L. D. Barron,

and L. D. Barron,

J. Am.

Sot.,

116 (1994)

3 (1994)

Biopolymers,

Chem.

Sot.,

443.

435. 34 (1994)

116 (19941 SISS.

303.