bolaform amides (Val)
 Valinyl bolaform amide


N,N'-Bis(t-buoxycarbonyl-valinyl)-diaminoethane 		2: 1 = 2 = L-Val
3: 1 = 2 = D-Val
4: 1 = L-Val, 2 = D-Val
5: 2 + 3 (1 : 1) mixture


Paper Mitsunobu Doi, Akiko Asano, Hiroyuki Yoshida, Mizue Inouguchi, Kazunori Iwanaga, Masahiro Sasaki, Yoshio Katsuya, Taizo Taniguchi and Daisuke Yamamoto
Structure and property of self-assemble valinyl bolaform amides having different chirality.
J. Peptide Res. 22, 1234-1234 (2005).
ABSTRACT: Bolaform amides were designed from N,N'-bis(carboethoxy-L-valinyl)-diaminoethane (1) by linking t-butyloxycarbonyl-valine through ethylenediamine (EDA) to enable spectroscopic and X-ray diffraction analyses. N,N'-Bis(Boc-L-valinyl)- diaminoethane (2) and N,N'-bis(Boc-D-valinyl)-diaminoethane (3) were composed of L-Val and D-Val, respectively. N-(Boc-L-valinyl)-N'-(Boc-D-valinyl)- diaminoethane (4) was composed of both L-Val and D-Val, and was achiral (meso-peptide). Peptide 5 was a 1:1 mixture of 2 and 3, and was also achiral (racemate). These peptides mediated gelation of corn oil at a concentration of approximately 1 %. Within crystals, the peptides formed β-sheet ribbons, but differences were observed in hydrogen-bonding patterns and side chain arrangements. These differences were also suggested from temperature dependence of amide protons. Force-field calculations based on the crystal structures indicated that association of β-sheet ribbons had energy benefits, and it was assumed that molecular aggregation spontaneously progressed. These results indicated the chirality of amino acids affected for the properties of bolaform amides.





2



4



5
Fig.1 β-sheet (crystal packing) and scanning electron microscopy

X-Ray summary for bolaform amides

  
Cmin, mg/g (gelation)
Tbot, K (melting)

Formula
Mr
System
Space group
a
b
c
β
V
Z

T, K
Dx
F(0 0 0)
Radiation
Wavelength
μ

NREF (obs)
Rint
NREF (used)
θmax

R
wR
(Δ/σ)max
Fraction θmax
Δρmax
Δρmin

PDB coord.
Packing x 40 mol

2: L-peptide 
9
397

C11H21N2O3
229.30
monoclinic
C2
23.175(4)
5.0727(8)
16.310(2)
133.751(2)
1385.0(4)
4

200.0(2)
1.100
500
Mo Kα
0.7107
0.080

6081
0.0231
1686
27.1

0.0367
0.0953
<0.001 
0.989 
0.157 
-0.139 

lval.pdb
L40.pdb

4: meso-peptide 
5
434

C22H42N4O6
458.60
monoclinic
P21/n
9.4514(3)
17.8546(8)
17.7242(9)
94.190(4)
2983.0(2)
2

223(2)
1.021
1000
SPring-8/BL24XU
0.834
0.074

8773
0.0232
4533
29.0

0.0419
0.1144
0.001 
0.926 
0.222
-0.153

mval.pdb
M40.pdb

5: racemate 
3
406

C11H21N2O3
229.30
tetragonal
P-42(1)c
17.1628(8)
17.1628(8)
9.7150(9)
90.0
2861.7(3)
4

220(2)
1.064
500
Mo Kα
0.7107
0.077

32814
0.0256
1781
27.1

0.0390
0.1084
0.008 
0.999 
0.183
-0.110

dlval.pdb
R40.pdb



Fig.2 Chemical shifts of amide protons.

Signal of amide proton EDA-NH of 4 is fairly shifted from those of 2 and 5, indicating the difference of H-bonds around EDA (Fig.1 center).

Fig.3 Typical DSC profile for decanol gels.

Temperature of peak bottom (Tbot) could be an index for thermostability. Endthermal ΔH of peaks a, b and c are measured for peptide concentrations.
 


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