24 Ultrastructureof Curdlan NOBUTAMI KASAI Department of Applied Chemistry, Faculty of Engineering, Osaka University, Yamadakami, Suita, Osaka 565 JAPAN TOKUYA HARADA
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Institute of Scientific and Industrial Research, Osaka University, Yamadakami, Suita, Osaka 565 JAPAN
1.
Introduction During the studies on Alcaligenes faeoalis var. myxogenes
10C3, Harada and co-workers found that a spontaneous mutant, 10C3K produces an insoluble exocellular polysaccharide (1).
This
polysaccharide i s entirely composed of D-glucosyl residues which are connected almost exclusively by
β-(1->3)-linkages.
This and
the similar glucan formed by some strains of Agrobacterium are named Curdlan because they form i r r e v e r s i b l y , r e s i l i e n t gel when heated i n water. Because of interesting and specific properties
of the g e l ,
curdlan has many potential uses not only i n food industry but also as a f i l m , a fiber, a support for immobilizing enzymes and a binding agent i n tobacco product etc. (2).
Besides these, an
antitumor activity(3) has been reported. In connection with these uses the conformation of curdlan molecule i n solution and i n gel and the ultrastructure of aggre gates of curdlan molecules are considered very important.
This
paper deals with conformational studies on curdlan molecules by means of l i g h t scattering,
13
C NMR, X-ray d i f f r a c t i o n , and
morphological studies using an electron microscope. 0-8412-0589-2/80/47-141-363$05.25/O © 1980 American Chemical Society In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
364
2.
1).
FIBER DIFFRACTION
Conformation of Curdlan Molecule in
METHODS
Solution
j
Conformation i n a cadoxen- water mixture (4) For the l i g h t
scattering
s t u d y , H i r a n o et al.
divided
a
c u r d l a n sample i n t o n i n e f r a c t i o n s by f r a c t i o n a l p r e c i p i t a t i o n a t 25°C w i t h c a d o x e n *
a s a s o l v e n t and a p r o p a n o l - w a t e r ( 3 : 1 b y volume)
m i x t u r e as a p r e c i p i t a n t .
The l i g h t
s c a t t e r i n g measurement
was
c a r r i e d o u t i n t h e 1:1 w a t e r - d i l u t e d c a d o x e n a t 25°C. From t h e m e a s u r e d s c a t t e r i n g
i n t e n s i t i e s H i r a n o et
al.
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o b t a i n e d t h e a n g u l a r dependence o f t h e i n f i n i t e - d i l u t i o n scattering
intensity
(K /RQ)^ O
of the zero-angle reduced then determined z-average
and t h e c o n c e n t r a t i o n d e p e n d e n c e
0
scattering
intensity
the values o f weight-average
2
(K /RQ)Q+Q.
They
Q
molecular weight
2
mean-square r a d i u s o f g y r a t i o n
coefficient A
reduced
*,
and s e c o n d
o f t h e f r a c t i o n by t h e u s u a l method.
The
M
y]9
virial
results
are presented i n Table I . The v a l u e s o b t a i n e d f o r
a r e about
one o r d e r o f m a g n i t u d e
l a r g e r than t h e r e p o r t e d number-average m o l e c u l a r w e i g h t s d e t e r m i n e d b y t h e method o f Manners et al. (5_) 2
Figure 1 g i v e s the molecular weight d a t a p o i n t s may be f i t t e d b y a s t r a i g h t 2
2
< 5 > | = 3.2 x 1 0 ~ M
d e p e n d e c e o f ^.
The
l i n e as shown i n F i g . 1. 0
-
W
5 3
( i n nm).
F i g u r e 1 i n c l u d e s t h e d a t a f r o m c e l l u l o s e i n t h e same s o l v e n t ( 7 ) . A t f i x e d Af , w
the values o f
f
f o r c u r d l a n a r e about
one
those f o r c e l l u l o s e , i n d i c a t i n g that the c u r d l a n molecule
assumes
a more c o i l e d f o r m t h a n d o e s t h e c e l l u l o s e m o l e c u l e i n 1:1 diluted
water-
cadoxen.
The d o u b l e - l o g a r i t h m i c p l o t s
of intrinsic viscosity
c u r d l a n ( 4 ) and c e l l u l o s e ( 6 ^ 7 ) a g a i n s t M and c e l l u l o s e m o l e c u l e s a r e n o t v e r y
*
half
T r i ( e t h y l e n e diamine) hydroxide,
w
[n] f o r
suggest t h a t t h e c u r d l a n
flexible.
[Cd(en) ](OH) 3
2
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
24.
Table I.
365
Ultrastructure of Curdlan
KASAI A N D H A R A D A
Numerical results from l i g h t scattering measurements on
curdlan fractions i n the 1:1 water-diluted cadoxen at 25°C(£)
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Fraction Number
M X10" w
5
2
n
X10 /cm
2
i4 X10Vcm
z
3
2
F-II
6 .83
1.62
3.81
F-III
5 .85
1.49
3.54
F-IV
3 .48
0.751
3.85
F-V
2 .60
0.534
4.38
F-VI
1 .78
0.350
3.71
F-VII
1 .24
0.262
6.58
F-VIII
0 .888
0.159
6.11
F-12-2*
0 .659
0.156
8.13
mol g "
2
*Sample f r a c t i o n a t e d a t T a k e d a C h e m i c a l I n d u s t r i e s . DPn 131 b y t h e method o f Manners et al. (5). —
Polymer Journal
Polymer Journal
Figure 1. Molecular weight dependence of < S > ^ for curdlan in the 1:1 waterdiluted cadoxen at 25°C (4). Data for cellulose (small circles) (1) are also plotted. 2
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
366
FIBER
DIFFRACTION
METHODS
A c o n s i d e r a t i o n o f t h e m o l e c u l a r c o n f o r m a t i o n u s i n g t h e worml i k e c h a i n model s u g g e s t s t h a t t h e c u r d l a n m o l e c u l e may c o n t a i n h e l i c a l p o r t i o n s b u t , as a whole, t a k e s a r a n d o m - c o i l
conformation
(£).
2).
Conformation i n an alkaline 1 3
F i g u r e 2 shows water
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C NMR s p e c t r a o f c u r d l a n ( D P n
540) o f an
s u s p e n s i o n and a l k a l i n e s o l u t i o n r e p o r t e d b y S a i t o et a£.(8).
I t i s noteworthy 1 3
solution
t h a t a t a c o n c e n t r a t i o n o f 0.22M NaOH t h e b r o a d
C NMR s i g n a l s d e c r e a s e t o l e s s t h a n o n e - t e n t h o f t h o s e o f t h e
aqueous s u s p e n s i o n .
T h i s sharp spectrum
random-coil conformation. Ogawa et aZ. ( 9 ) .
This i s consistent with the results of
They d e t e r m i n e d
rotation, intrinsic
i s characteristic of
t h e dependence o f o p t i c a l
v i s c o s i t y , and t h e e x t i n c t i o n a n g l e o f
c u r d l a n s o l u t i o n on c o n c e n t r a t i o n o f NaOH and f o u n d t h e t r a n s i t i o n from o r d e r e d form t o r a n d o m - c o i l
3.
1).
Conformation
i n a b o u t 0.2M.
o f C u r d l a n M o l e c u l e s i n Gel
Conformation i n gel. S a i t o et al.(S) h a v e shown t h a t
observed 2.8,
( F i g . 3B).
1 3
1 3
C NMR s i g n a l s o f g e l c a n be
C peak p o s i t i o n s a r e s h i f t e d d o w n f i e l d b y
3.2, and 0.9 f o r C - l , C-3, and C-4 r e s p e c t i v e l y ,
w i t h those o f w a t e r - s o l u b l e degraded conformation.
compared
polymer i n a random-coil
On t h e o t h e r h a n d , o t h e r C-2, C-5, and C-6 s i g n a l s
remain unchanged.
T h e s e d o w n f i e l d d i s p l a c e m e n t s o f t h e C - l and
C-3 s i g n a l s o c c u r a t c a r b o n s p a r t i c i p a t i n g i n t h e g l u c o s i d i c l i n k a g e s o f (1+3)-$-D-glucan, terms o f a c e r t a i n f i x e d The
and t h i s f a c t c o u l d be e x p l a i n e d i n
conformation.
e n e r g e t i c a l l y p r e f e r r e d c o n f o r m a t i o n s o f (1+3)-$-D-glucan
have been d e t e r m i n e d by S u n d a r a l i n g h a m ( 1 0 ) , and S a t h y a n a r a y a n a and e x t e n d e d shwon t h a t
1 3
and R a o ( 1 2 ) .
helical
Rees and S c o t t ( 1 1 ) ,
According t o these r e s u l t s ,
c o n f o r m a t i o n s a r e most p r o b a b l e .
C peaks o f m o l e c u l e s
wide
I t has been
i n the r i g i d double- o r t r i p l e -
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
24.
KASAI AND HARADA
helical narrow
conformation are completely
1 3
C peaks have been r e p o r t e d
(16,17). should
The are
lost(13-15).
1 3
C NMR v i s i b l e
t othe s i n g l e - h e l i c a l
l i n e w i d t h s o f C-1--C-5
1 3
However, r a t h e r
f o rsingle helical
These f a c t s suggest t h a t t h e
be a s c r i b e d
367
Vltrastructure of Curdlan
molecules portion
region.
C resonance peaks i n t h e g e l
a b o u t 150 H z , w h i c h a r e r a t h e r b r o a d i n c o m p a r i s o n w i t h
those
o f a l k a l i n e s o l u t i o n (0.22M N a O H ) ( F i g . 2D) a n d a l s o w i t h t h o s e o f the
lower molecular weight f r a c t i o n ( F i g . 3A).
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i n t e g r a t e d peak i n t e n s i t i e s pressed) with
(with nuclear
Overhauser e f f e c t s u r -
t h o s e o f t h e c o r r e s p o n d i n g p e a k s i n t h e 0.22M NaOH
s o l u t i o n , i n which the curdlan
molecules are considered
r a n d o m - c o i l c o n f o r m a t i o n , i t was e s t i m a t e d 1 3
C
By c o m p a r i n g t h e
peaks account f o r o n l y
carbons o f t h e t o t a l
i n v i s i b l e portion o f the
zones o f t h e g e l n e t work
that these observed
20-30 and 6 0 % f o r t h e C-1--C-5 a n d C-6
gel, respectively. 1 3
t o have
C should
Hence, t h e r e m a i n i n g
be a s c r i b e d t o t h e j u n c t i o n
and t o r e s i d u e s
located closelyt o
these junctions. These r e s u l t s l e a d t o a c o n c l u s i o n
that the v i s i b l e
p e a k s a r e due t o t h e s i n g l e h e l i c a l p o r t i o n .
C NMR
The N M R - i n v i s i b l e
p o r t i o n o f the g e l i s present as m u l t i - h e l i c a l 2).
1 3
junction-zones.
Conformation i n and u l t r a s t r u c t u r e o f a n o r i e n t e d g e l . As
t h e X - r a y d i f f r a c t i o n d i a g r a m s o f a n o r i e n t e d g e l ( F i g . 6)
are p o o r l y crystal
crystalline,
i t has been u s e f u l t o conduct
X-ray
s t r u c t u r e a n a l y s e s o f o l i g o m e r o f 3-(1+3)-D-glucan.
molecular structures o f laminarabiose
The
and i t s a c e t y l d e r i v a t i v e
have been d e t e r m i n e d . (1) L a m i n a r a b i o s e (18) As
shown i n F i g . 4, t h e m o l e c u l e s o f l a m i n a r a b i o s e
have a
c o n f o r m a t i o n , d i f f e r e n t from t h e f u l l y - e x t e n d e d one, which i s s t a b i l i z e d by an i n t r a m o l e c u l a r
f
h y d r o g e n b o n d b e t w e e n 0-4 --H a n d
o
«
0 - 5 [ 2 . 7 8 6 ( 7 ) A] {Cf. i n t r a m o l e c u l a r
0-2
r i n g - t o - r i n g confromation can be d e s c r i b e d -37.5°) a c c o r d i n g
f
0 - 2 = 3 . 9 2 0 ( 6 ) A ) . The a s ( $ , ¥ ) = (27.9°,
t o t h e d e f i n i t i o n o f S a t h y a n a r a y a n a and R a o ( 1 2 ) ,
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
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368
FIBER
120
100
80
60
DIFFRACTION
40PPm
METHODS
0 Biochemistry
Figure 2.
13
C NMR spectra of curdlan(DPn 540) in water suspension (A) and alkaline solution (90° pulse, repetition time 0.6 s) ($)
B
C u r d l a n ( D P n 540)
A
Degraded
C-4 C-2
polymer
C-6
C-3
C-l
-J
110
100
90
80
70
60
L_
50 ppm(TMS) Biochemistry
13
Figure 3. C NMR spectra of curdlan and of a degraded polymer (DPn 13) in solution (90° pulse, repetition times 1 s for A and 0.6 s for B) (8)
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
24.
KASAI AND HARADA
369
Ultrastructure of Curdlan
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H(C-6-2)
fHc-e'-i)
^(0-4')
H
!7H(C-6-l)
(C-5)(
H(C-5')£
/0-1'B H(C-2)
0-1 a
1
H(O-l'a) Ha(C-l')
0-W
Carbohydrate Research
Figure 4.
Molecular structure of laminarabiose (IS)
The C and O atoms are shown as thermal ellipsoids with 50% probability level, and the H atoms are represented as spheres with B = 0.75 A . Atoms that are related to the a-anomer molecule (~38%) and the water of crystallization (~19%) associated with the a-anomer molecules are shown in squares. 2
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
370
and
FIBER DIFFRACTION
METHODS
i t i s l o c a t e d i n t h e c o m p a r a t i v e l y low e n e r g y r e g i o n o f
energy contour diagram o f
the
B-(1+3)-glucan(12).
1
(2) M e t h y l
2,3,4,6,2 ,4',6'-hepta-tf-acetyl-$-l>laminarabioside(19).
B e c a u s e h y d r o g e n bonds a r e p r o h i b i t e d by t h e a c e t y l the molecules
have a f u l l y - e x t e n d e d c o n f o r m a t i o n 1
and
groups
the
inter-
1
o x y g e n d i s t a n c e s a r e 0-4 •••-0-5=3.224(14) and
0-2 •••-0-2=3.604
o
(14) A ( F i g . 5 ) . as
The
r i n g - t o - r i n g conformation
($ ,V) = (42.5°, 4.7°),
and
can be
described
i t i s a l s o l o c a t e d i n the
other
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c o m p a r a t i v e l y low e n e r g y r e g i o n i n t h e e n e r g y c o n t o u r m a p ( 1 2 ) . (3)
Curdlan
a.
Room temperature
structure
T a k e d a et al.(20)
prepared
a
f i l m s p e c i m e n , r e g e n e r a t i n g f r o m a IN NaOH s o l u t i o n o f c u r d l a n (DPn=400).
T h i s f i l m was
A f i b r o u s s p e c i m e n was uniaxially
s w o l l e n i n w a t e r a t room
o b t a i n e d by s t r e t c h i n g t h e s w o l l e n
(draw r a t i o 3.5 : 1 ) .
o f t h e wet,
has a c r o s s - l i k e
t h e l a y e r s 0, 3, and 4.
appearance
average
2 were much w e a k e r t h a n t h o s e
A t o t a l o f 17 o b s e r v e d
be i n d e x e d by an o r t h o r h o m b i c
diagram
molecule.
f e a t u r e o f the diagram i s t h a t the
o f t h e l a y e r s 1 and
film
center o f the f i b e r
a simple h e l i c a l s t r u c t u r e f o r the
Another s i g n i f i c a n t intensities
The
f i b r o u s s p e c i m e n ( F i g . 6A)
that suggests
temperature.
reflections
of
could
u n i t c e l l w i t h a=26.4, fr=16.4 and
o
£=22.65 A n o t be
( f i b e r a x i s ) ; but the c o r r e s p o n d i n g
space group c o u l d
determined.
R e f e r r i n g t o a c y l i n d r i c a l P a t t e r s o n f u n c t i o n a l ) computed from the i n t e n s i t y
distribution
o f t h e f i b e r d i a g r a m , and
also
c o n s i d e r i n g the s t a n d a r d geometry o f the D-glucose r i n g ( 2 2 ) conformations crystal
a b o u t t h e 3-(1+3) l i n k a g e o b t a i n e d by t h e
s t r u c t u r e analyses of laminarabiose(18)
d e r i v a t i v e ( 1 9 ) , r e a s o n a b l e m o d e l s o f 7/1
and 6/1
and
and
single
i t s acetyl
single
helices
o
w i t h f i b e r r e p e a t p e r i o d o f 2 2 . 6 5 A ( f u l l y - e x t e n d e d model) c o u l d be c o n s t r u c t e d .
The
F o u r i e r t r a n s f o r m o f each h e l i x
was
c a l c u l a t e d u s i n g t h e e q u a t i o n g i v e n by K l u g et al.(23). results
The
f o r the r e l a t i v e magnitude o f the i n t e n s i t i e s o f the
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
7/1
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24.
KASAI AND HARADA
Ultrastructure of Curdlan
371
Carbohydrate Research
Figure 5. Molecular structure of methyl 2,3,4,6,2',4',6'-hepata-O-acetyl-p-vlaminarabioside (19). The upper ring is glycosidic residue. Shaded and nonshaded ellipsoids, and small spheres represent C, O, and H atoms, respectively.
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
FIBER
DIFFRACTION
METHODS
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372
Figure 6. The variation of x-rayfiberdiagrams of the wet, fibrous curdlan specimen (DPn 400) dried in the air (20). Starting from the original gel specimen (A), photographs from (B)to(E) were taken at regular intervals (1 hr).
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
24.
KASAI AND
HARADA
Ultrastructure of Curdlan
single helix, either left-
373
o r right-handed, agree w i t h
o b s e r v e d peak p o s i t i o n s o f t h e
the
l a y e r s 0, 1, 2, a n d 3 b e t t e r
t h o s e o f 6/1 s i n g l e h e l i c e s .
However, t h e
o f l a y e r s 1 and 2 are
than the observed i n t e n s i t i e s .
greater
F o u r i e r t r a n s f o r m s o f t h e d o u b l e - and were a l s o c a l c u l a t e d u s i n g
the
the observed i n t e n s i t y .
intensities The
t r i p l e - s t r a n d e d 7/1 h e l i c e s
equation
Among them, t h a t o f a t r i p l e - h e l i x
calculated
than
given by Fraser
et al. (24).
showed a r a t h e r good f i t w i t h
However, t h e
calculated intensities o f
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l a y e r s 1 a n d 2 a r e v e r y weak, b e i n g a b o u t o n e - h u n d r e d t h o f t h a t at the
equator.
T h e s e f a c t s s u g g e s t t h a t t h e most o f t h e
3 - D - g l u c a n m o l e c u l e i n t h e w e t f i b r o u s s p e c i m e n has helical
s t r u c t u r e and
structure
(Fig. 8).
t h e r e s t has
posed s t r u c t u r e b a s e d on t h e The
X-ray small-angle
a 7/1 s i n g l e
a triple-stranded helical
These r e s u l t s are 1 3
(1-K5)-
c o n s i s t e n t w i t h the
C NMR s t u d i e s m e n t i o n e d
before.
s c a t t e r i n g photograph o f the
s p e c i m e n shows o n l y a d i f f u s e s t r e a k
along
Assuming t h a t the
inhomogeneties i n the
highly dispersed,
uniform, long
arranged p a r a l l e l
t o the
the
pro-
equator
same (Fig.
7).
specimen c o n s i s t s o f
c y l i n d r i c a l m i c e l l e s which
are
s t r e t c h i n g d i r e c t i o n , the diameter o f o
t h e m i c e l l e s was e s t i m a t e d plot(25)
o f the
2
e T-e p l o t ( 2 6 )
t o b e a b o u t 80 A b y t h e
i n t e n s i t y d i s t r i b u t i o n along gives
the
Guinier
equator.
The
a measure o f i n t e r m i c e l l a r d i s t a n c e i n
the
o
e q u a t o r a s a b o u t 120 A. A v a r i a t i o n o f f i b e r diagram, taken a t r e g u l a r i n t e r v a l s , o f a wet
f i b r o u s specimen d r i e d i n the
also given
i n F i g . 6(20).
During the
broadening o f each p a t t e r n destroyed the
f i b e r d i a g r a m s , and
s c a t t e r i n g weakened and
a i r a t room t e m p e r a t u r e , i s
parallel
course o f drying, t h e more and
more t h e d e t a i l s o f
t o t h i s change t h e
f i n a l l y disappeared.
small-angle
These f a c t s suggest
that the m i c e l l e s l o s e i n t r a m i c e l l a r w a t e r ( o r c r y s t a l l i n e by
water)
d r y i n g , which d i s t u r b s the r e g u l a r m o l e c u l a r arrangement
i n s i d e t h e m i c e l l e , and
a t the
same t i m e ,
the
evaporation
m i c e l l a r water causes adjacent m i c e l l e s t o contact
o f inter-
d i r e c t l y , which
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
374
FIBER
DIFFRACTION
METHODS
Polymer Journal
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Figure 7. X-ray small-angle scattering diagram of the wet, fibrous curdlan specimen (DPn 400) (20)
7/1
Helix
Structure of A Micelle
U l t r e s t r u c t u r e o f An O r i e n t e d Gel (Room Temperature)
Figure 8.
A model for the ultrastructure of curdlan gel at room temperature.
The oriented gel consists of micelles, of which the average diameter is about 80 A. Micelle-micelle distance is about 120 A. Area between micelles is filled with water molecules. Micelle interior is packed mostly by 7/1 single helical molecules that are hydrogenbonded to one another by water molecules. The single helical molecule is also probably hydrated. Some parts of the micelle are occupied by molcules of triple-stranded helix, which are also hydrated to some extent.
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
24.
KASAI AND HARADA
Ultrastructure of Curdlan
does away w i t h t h e i n h o m o g e n e i t y b. High temperature
i n t h e specimen
375
(Fig. 8).
structure
M a r c h e s s a u l t et al. (27) o b t a i n e d w e a k l y c r y s t a l l i n e a n d o r i e n t e d f i b e r s ( A ) b y e x t r u d i n g a 1 0 % DMSO s o l u t i o n o f c r u d l a n i n t o CH3OH a t room t e m p e r a t u r e a n d w a s h i n g
i ti n water.
f o u n d t h a t t h e same f i b e r a n n e a l e d i n w a t e r , u n d e r
They
tension, at
140°C, i n a s e a l e d bomb, i s o f h i g h e r c r y s t a l l i n i t y a n d o c c u r e d as two r e v e r s i b l e c r y s t a l l i n e p o l y m o r p h s :
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h u m i d i t y ( B ) and t h e o t h e r a t h u m i d i t i e s
one a t h i g h
relative
l e s s than 20%(C).
o
The
f i b e r p e r i o d o f 5.79 A f o r (C) t o g e t h e r w i t h t h e r e s u l t s
o f a c o n f o r m a t i o n a l study and t h e v a l u e s o f i t s i n t e n s i t y p o i n t e d t o a t r i p l e - s t r a n d e d 6/1 h e l i c a l T a k e d a et al.(19)
s t r u c t u r e w i t h P6
3
h e a t - t r e a t e d t h e wet f i b r o u s specimen
s e a l e d bomb i n t h e p r e s e n c e o f w a t e r . 120°C t h e a n n e a l e d s p e c i m e n f i b e r diagram
Figure 9.
symmetry
A t temperatures
above
showed a r e m a r k a b l y d i f f e r e n t
(Fig. 9): thef i r s t
ina
X-ray
layer disappered, the f i b e r
X-ray fiber diagrams of heat-treated (>120°C) curdlan specimen (TJFn 400) (20): (A) dried in air and (B) dried in vacuum
In Fiber Diffraction Methods; French, Alfred D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
376
FIBER
period decreased t o 18.1 A .
DIFFRACTION
METHODS
The a n n e a l e d s p e c i m e n d r i e d i n
2
o
vacuum gave a n o t h e r X - r a y d i a g r a m , h a v i n g a f i b e r p e r i o d o f 5 . 7 A 2
(Table I I ) .
T h e s e two k i n d s o f f i b e r d i a g r a m s
respectively
c o r r e s p o n d t o t h o s e o f (B) and (C) o b t a i n e d b y M a r c h e s s a u l t et al. (27). Triple-stranded helical
s t r u c t u r e was a l s o p r o p o s e d f o r B-
( l + 3 ) - D - g l u c a n b y A t k i n s and P a r k e r ( 2 8 ) .
Blum and S a r k o ( 2 9 )
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s t u d i e d the s t r u c t u r e s o f l e n t i n a n , a branched and o f pachyman, a ( 1 + 3 ) - B - D - g l u c a n sidic
(1+3)-B-D-glucan
c o n t a i n i n g a few B - l , 6 - g l u c o -
l i n g a k e s , and p r o p o s e d t h e e x i s t n e c e o f a t r i p l e - s t r n a d e d
helix i n their
structures.
C r y s t a l d a t a and a b r i e f a c c o u n t f o r t h e s t r u c t u r e o f t h r e e forms o f t h e c u r d l a n a r e g i v e n i n T a b l e I I . A schematic r e p r e s e n -
T a b l e I I . A b r i e f account f o r t h e s t r u c t u r e o f t h r e e forms o f Curdlan Room t e m p e r a t u r e or Heat-treated a t temp^.120°C i n a s e a l e d bomb i n the presence o f water, and d r i e d i n a i r d r i e d i n vacuum s
a=b=lSAi
A
o
=Z?= 1 4 . 1
a
A
9
fc=16.4