organic compounds
L-Leucylglycylglycine
aInstitute of Radioisotope Research, St. Marianna University Graduate School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan, bDepartment of Molecular and Behavioral Neuroscience, St. Marianna University Graduate School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8511, Japan, and cSchool of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan
*Correspondence e-mail: m_ootaki@marianna-u.ac.jp
In the title compound, C10H19N3O4, the N- and C-termini are protonated and ionized, respectively, and the molecule forms a zwitterion. The main chain is in a folded form. In the crystal, the N-terminal –NH3+ group hydrogen bonds to three C-terminal –COO groups and one carbonyl O atom, forming a three-dimensional network. In addition, an N—H⋯O hydrogen bond between the amide groups of the middle glycine residue and a C—H⋯O interaction continue along the a-axis direction. The side chains of the leucyl residues form a hydrophobic region along the a axis.
Related literature
For related structures of L-leucylglycylglycine, see: Goswami et al. (1977); Srikrishnan & Parthasarathy (1987); Kiyotani & Sugawara (2012).
Experimental
Crystal data
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Data collection: CrystalClear (Rigaku, 2006); cell CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and Yadokari-XG 2009 (Kabuto et al., 2009).
Supporting information
https://doi.org/10.1107/S1600536813008490/is5257sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813008490/is5257Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536813008490/is5257Isup3.cml
L-Leucylglycylglycine was purchased from Bachem Inc. Single crystals were obtained from an aqueous solution.
H atoms were placed in calculated positions with C—H = 0.98 Å (CH3), 0.99 Å (CH2) or 1.00 Å (CH) and refined in a riding mode with Uiso(H) = 1.2Ueq(C). The other H atoms were placed in a difference Fourier map. The N-terminal H atoms were restrained to N—H = 0.87 (4) Å during refinements. The
was known for the purchased material.A moderately large number of ═C) are formed along the a axis. The hydrophobic region composed of leucyl side chains is surrounded by hydrophilic parts, and forms a column along the a axis.
are biologically active, and their structures are investigated to facilitate the determination of the possible conformations of oligopeptide and polypeptide chains. The N-terminus and C-terminus of L-leucylglycylglycine (L-LGG) are protonated and ionized, respectively, and the molecule is a zwitterion (Fig. 1). The main chain is in a folded form. The torsion angles of C2—N2—C3—C4 and N2—C3—C4—N3 are -87.54 (18)° and -52.78 (19)°, respectively. The N-terminal –NH3+ groups and the C-terminal –COO- groups form hydrogen bond networks (Fig. 2 & Fig. 3). One of the hydrogen atoms of the –NH3 group forms a three-centered hydrogen bond with the carboxyl and carboxyl oxygen atoms. In addition, intermolecular hydrogen bonds among amide groups (NH···OIn the case of the L-leucylglycylglycylglycine (Srikrishnan & Parthasarathy, 1987), the main chain is a folded form, and hydrophobic columns are formed along the a axis as in the case of L-LGG. On the other hand, the main chain of D,L-leucylglycylglycine (D,L-LGG) (Goswami et al., 1977) is in a nearly all-trans form expect the N-terminus. The main chains align parallel to the b axis in a head-to-tail manner and a β-sheetlike structure is formed parallel to the bc plane. The hydrophobic regions of the leucyl side chains and the hydrophilic regions are aligned alternately along the a axis. As in the case of D,L-LGG, the main chain in L-leucylglycine 0.67 hydrate (Kiyotani & Sugawara, 2012) is in a extended form, and hydrophobic and hydrophilic regions are aligned alternately along the c axis.
For related structures of L-leucylglycylglycine, see: Goswami et al. (1977); Srikrishnan & Parthasarathy (1987); Kiyotani & Sugawara (2012).
Data collection: CrystalClear (Rigaku, 2006); cell
CrystalClear (Rigaku, 2006); data reduction: CrystalClear (Rigaku, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and Yadokari-XG 2009 (Kabuto et al., 2009).Fig. 1. View of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at 50% probability level and H atoms are shown as small spheres of arbitrary radii. | |
Fig. 2. Packing diagram of the title compound viewed along the a axis. Hydrophobic columns are indicated by green circles. | |
Fig. 3. Hydrogen bonding scheme around the molecule, whose carbon atoms are colored with black. Hydrogen bonds are indicated by dotted lines. Side-chain atoms of the leucyl residues have been omitted for clarity. |
C10H19N3O4 | F(000) = 528 |
Mr = 245.28 | Dx = 1.288 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71070 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 949 reflections |
a = 5.391 (5) Å | θ = 7.6–17.5° |
b = 11.742 (10) Å | µ = 0.10 mm−1 |
c = 19.975 (16) Å | T = 173 K |
V = 1264.4 (19) Å3 | Block Rod, colorless |
Z = 4 | 0.48 × 0.18 × 0.08 mm |
Rigaku Mercury CCD area-detecter diffractometer | 2200 reflections with I > 2σ(I) |
Radiation source: rotating anode | Rint = 0.070 |
Graphite monochromator | θmax = 27.5°, θmin = 3.5° |
ω scans | h = −6→6 |
9374 measured reflections | k = −15→15 |
2887 independent reflections | l = −21→25 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.96 | w = 1/[σ2(Fo2) + (0.0374P)2] where P = (Fo2 + 2Fc2)/3 |
2887 reflections | (Δ/σ)max = 0.012 |
176 parameters | Δρmax = 0.14 e Å−3 |
3 restraints | Δρmin = −0.17 e Å−3 |
C10H19N3O4 | V = 1264.4 (19) Å3 |
Mr = 245.28 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 5.391 (5) Å | µ = 0.10 mm−1 |
b = 11.742 (10) Å | T = 173 K |
c = 19.975 (16) Å | 0.48 × 0.18 × 0.08 mm |
Rigaku Mercury CCD area-detecter diffractometer | 2200 reflections with I > 2σ(I) |
9374 measured reflections | Rint = 0.070 |
2887 independent reflections |
R[F2 > 2σ(F2)] = 0.038 | 3 restraints |
wR(F2) = 0.087 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.96 | Δρmax = 0.14 e Å−3 |
2887 reflections | Δρmin = −0.17 e Å−3 |
176 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
N1 | −0.1744 (3) | 0.64554 (12) | 0.49670 (7) | 0.0348 (3) | |
N2 | −0.0484 (3) | 0.64749 (12) | 0.67001 (6) | 0.0315 (3) | |
H5 | −0.195 (4) | 0.6402 (15) | 0.6825 (9) | 0.036 (5)* | |
N3 | 0.1814 (3) | 0.52895 (12) | 0.78349 (7) | 0.0362 (3) | |
H8 | 0.022 (4) | 0.5354 (16) | 0.7880 (9) | 0.048 (6)* | |
O1 | 0.2239 (2) | 0.64148 (11) | 0.58454 (5) | 0.0415 (3) | |
O2 | 0.5246 (2) | 0.62376 (11) | 0.75146 (6) | 0.0485 (3) | |
C1 | −0.1911 (3) | 0.58011 (12) | 0.56075 (8) | 0.0290 (3) | |
H4 | −0.3570 | 0.5921 | 0.5820 | 0.035* | |
C2 | 0.0137 (3) | 0.62595 (12) | 0.60611 (7) | 0.0273 (3) | |
C3 | 0.1320 (3) | 0.69772 (14) | 0.71523 (8) | 0.0368 (4) | |
H6 | 0.0422 | 0.7431 | 0.7493 | 0.044* | |
H7 | 0.2381 | 0.7507 | 0.6894 | 0.044* | |
C4 | 0.2975 (3) | 0.61277 (13) | 0.75092 (7) | 0.0314 (4) | |
C5 | 0.3059 (3) | 0.45098 (16) | 0.82883 (9) | 0.0406 (4) | |
H9 | 0.4550 | 0.4883 | 0.8477 | 0.049* | |
H10 | 0.3604 | 0.3826 | 0.8038 | 0.049* | |
C6 | 0.1333 (4) | 0.41541 (13) | 0.88559 (8) | 0.0354 (4) | |
O3 | 0.2277 (3) | 0.35522 (11) | 0.93090 (6) | 0.0536 (4) | |
O4 | −0.0855 (3) | 0.44525 (12) | 0.88306 (7) | 0.0545 (4) | |
C7 | −0.1526 (3) | 0.45349 (13) | 0.54488 (8) | 0.0374 (4) | |
H11 | −0.2711 | 0.4312 | 0.5094 | 0.045* | |
H12 | 0.0168 | 0.4434 | 0.5267 | 0.045* | |
C8 | −0.1855 (4) | 0.37232 (14) | 0.60441 (9) | 0.0413 (4) | |
H13 | −0.0679 | 0.3959 | 0.6406 | 0.050* | |
C9 | −0.1199 (5) | 0.25116 (15) | 0.58278 (10) | 0.0636 (7) | |
H14 | −0.1379 | 0.1995 | 0.6210 | 0.076* | |
H15 | 0.0518 | 0.2492 | 0.5667 | 0.076* | |
H16 | −0.2316 | 0.2272 | 0.5467 | 0.095* | |
C10 | −0.4475 (5) | 0.3769 (2) | 0.63228 (13) | 0.0715 (7) | |
H17 | −0.5664 | 0.3609 | 0.5964 | 0.086* | |
H18 | −0.4796 | 0.4529 | 0.6507 | 0.086* | |
H19 | −0.4656 | 0.3199 | 0.6678 | 0.086* | |
H1 | −0.011 (5) | 0.636 (2) | 0.4768 (12) | 0.089 (9)* | |
H2 | −0.284 (5) | 0.6147 (19) | 0.4666 (12) | 0.076 (7)* | |
H3 | −0.202 (4) | 0.7193 (16) | 0.5047 (11) | 0.058 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.0420 (9) | 0.0301 (7) | 0.0322 (7) | −0.0012 (7) | −0.0133 (7) | 0.0028 (6) |
N2 | 0.0312 (8) | 0.0404 (8) | 0.0228 (6) | −0.0052 (7) | 0.0020 (6) | 0.0025 (6) |
N3 | 0.0288 (8) | 0.0458 (8) | 0.0341 (7) | −0.0020 (7) | 0.0000 (6) | 0.0152 (6) |
O1 | 0.0248 (6) | 0.0666 (8) | 0.0332 (6) | −0.0019 (6) | 0.0030 (5) | 0.0004 (6) |
O2 | 0.0387 (8) | 0.0668 (9) | 0.0399 (7) | −0.0099 (7) | 0.0061 (5) | 0.0128 (6) |
C1 | 0.0284 (8) | 0.0304 (7) | 0.0282 (8) | 0.0006 (7) | −0.0021 (7) | 0.0001 (6) |
C2 | 0.0272 (8) | 0.0294 (8) | 0.0253 (7) | 0.0018 (7) | 0.0018 (6) | 0.0038 (6) |
C3 | 0.0496 (12) | 0.0340 (8) | 0.0268 (8) | −0.0083 (8) | −0.0054 (8) | 0.0034 (7) |
C4 | 0.0375 (10) | 0.0396 (9) | 0.0172 (7) | −0.0051 (8) | 0.0031 (7) | 0.0006 (6) |
C5 | 0.0365 (10) | 0.0480 (10) | 0.0373 (9) | 0.0046 (9) | 0.0010 (8) | 0.0148 (8) |
C6 | 0.0498 (11) | 0.0301 (8) | 0.0264 (8) | −0.0120 (8) | −0.0017 (8) | 0.0028 (7) |
O3 | 0.0698 (9) | 0.0532 (7) | 0.0379 (7) | −0.0196 (7) | −0.0195 (7) | 0.0220 (6) |
O4 | 0.0427 (8) | 0.0644 (9) | 0.0562 (8) | 0.0010 (7) | 0.0156 (7) | 0.0178 (7) |
C7 | 0.0482 (11) | 0.0303 (8) | 0.0338 (9) | 0.0007 (8) | −0.0012 (8) | −0.0004 (7) |
C8 | 0.0532 (11) | 0.0325 (8) | 0.0381 (9) | −0.0025 (9) | −0.0036 (8) | 0.0037 (8) |
C9 | 0.096 (2) | 0.0342 (10) | 0.0602 (14) | 0.0078 (10) | 0.0029 (13) | 0.0088 (9) |
C10 | 0.0713 (16) | 0.0552 (13) | 0.0882 (17) | −0.0017 (12) | 0.0223 (13) | 0.0234 (12) |
N1—C1 | 1.495 (2) | C5—C6 | 1.525 (3) |
N1—H1 | 0.97 (2) | C5—H9 | 0.9900 |
N1—H2 | 0.92 (2) | C5—H10 | 0.9900 |
N1—H3 | 0.894 (19) | C6—O4 | 1.232 (3) |
N2—C2 | 1.344 (2) | C6—O3 | 1.256 (2) |
N2—C3 | 1.452 (2) | C7—C8 | 1.534 (2) |
N2—H5 | 0.83 (2) | C7—H11 | 0.9900 |
N3—C4 | 1.336 (2) | C7—H12 | 0.9900 |
N3—C5 | 1.452 (2) | C8—C10 | 1.519 (3) |
N3—H8 | 0.87 (2) | C8—C9 | 1.528 (3) |
O1—C2 | 1.226 (2) | C8—H13 | 1.0000 |
O2—C4 | 1.231 (2) | C9—H14 | 0.9800 |
C1—C2 | 1.526 (2) | C9—H15 | 0.9800 |
C1—C7 | 1.534 (2) | C9—H16 | 0.9800 |
C1—H4 | 1.0000 | C10—H17 | 0.9800 |
C3—C4 | 1.516 (2) | C10—H18 | 0.9800 |
C3—H6 | 0.9900 | C10—H19 | 0.9800 |
C3—H7 | 0.9900 | ||
C1—N1—H1 | 110.2 (15) | C6—C5—H9 | 109.5 |
C1—N1—H2 | 108.6 (14) | N3—C5—H10 | 109.5 |
H1—N1—H2 | 105 (2) | C6—C5—H10 | 109.5 |
C1—N1—H3 | 109.6 (14) | H9—C5—H10 | 108.1 |
H1—N1—H3 | 110 (2) | O4—C6—O3 | 125.31 (17) |
H2—N1—H3 | 113 (2) | O4—C6—C5 | 118.43 (16) |
C2—N2—C3 | 120.03 (15) | O3—C6—C5 | 116.25 (18) |
C2—N2—H5 | 120.0 (13) | C8—C7—C1 | 115.23 (14) |
C3—N2—H5 | 119.4 (13) | C8—C7—H11 | 108.5 |
C4—N3—C5 | 123.47 (17) | C1—C7—H11 | 108.5 |
C4—N3—H8 | 116.8 (13) | C8—C7—H12 | 108.5 |
C5—N3—H8 | 116.7 (13) | C1—C7—H12 | 108.5 |
N1—C1—C2 | 106.45 (13) | H11—C7—H12 | 107.5 |
N1—C1—C7 | 108.24 (13) | C10—C8—C9 | 110.59 (17) |
C2—C1—C7 | 111.49 (13) | C10—C8—C7 | 111.68 (16) |
N1—C1—H4 | 110.2 | C9—C8—C7 | 109.41 (15) |
C2—C1—H4 | 110.2 | C10—C8—H13 | 108.4 |
C7—C1—H4 | 110.2 | C9—C8—H13 | 108.4 |
O1—C2—N2 | 122.41 (14) | C7—C8—H13 | 108.4 |
O1—C2—C1 | 120.84 (14) | C8—C9—H14 | 109.5 |
N2—C2—C1 | 116.75 (14) | C8—C9—H15 | 109.5 |
N2—C3—C4 | 114.79 (14) | H14—C9—H15 | 109.5 |
N2—C3—H6 | 108.6 | C8—C9—H16 | 109.5 |
C4—C3—H6 | 108.6 | H14—C9—H16 | 109.5 |
N2—C3—H7 | 108.6 | H15—C9—H16 | 109.5 |
C4—C3—H7 | 108.6 | C8—C10—H17 | 109.5 |
H6—C3—H7 | 107.5 | C8—C10—H18 | 109.5 |
O2—C4—N3 | 122.62 (16) | H17—C10—H18 | 109.5 |
O2—C4—C3 | 121.36 (15) | C8—C10—H19 | 109.5 |
N3—C4—C3 | 115.97 (17) | H17—C10—H19 | 109.5 |
N3—C5—C6 | 110.74 (16) | H18—C10—H19 | 109.5 |
N3—C5—H9 | 109.5 | ||
C3—N2—C2—O1 | 4.0 (2) | N2—C3—C4—O2 | 129.75 (17) |
C3—N2—C2—C1 | −176.27 (13) | N2—C3—C4—N3 | −52.78 (19) |
N1—C1—C2—O1 | −45.43 (19) | C4—N3—C5—C6 | 147.06 (16) |
C7—C1—C2—O1 | 72.41 (19) | N3—C5—C6—O4 | 7.0 (2) |
N1—C1—C2—N2 | 134.83 (14) | N3—C5—C6—O3 | −174.41 (14) |
C7—C1—C2—N2 | −107.33 (16) | N1—C1—C7—C8 | −175.12 (14) |
C2—N2—C3—C4 | −87.54 (18) | C2—C1—C7—C8 | 68.14 (19) |
C5—N3—C4—O2 | 7.5 (2) | C1—C7—C8—C10 | 62.1 (2) |
C5—N3—C4—C3 | −169.93 (15) | C1—C7—C8—C9 | −175.13 (17) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O3i | 0.97 (3) | 1.78 (3) | 2.743 (2) | 168 (2) |
N1—H2···O4ii | 0.92 (2) | 1.94 (2) | 2.822 (2) | 160 (2) |
N1—H2···O3ii | 0.92 (2) | 2.52 (2) | 3.260 (2) | 138 (2) |
N1—H3···O1iii | 0.89 (2) | 2.45 (2) | 3.031 (2) | 123 (2) |
N1—H3···O3iv | 0.89 (2) | 2.05 (2) | 2.870 (2) | 151 (2) |
N2—H5···O2v | 0.83 (2) | 2.05 (2) | 2.832 (2) | 155 (2) |
C1—H4···O1v | 1.00 | 2.33 | 3.269 (2) | 155 |
Symmetry codes: (i) −x+1/2, −y+1, z−1/2; (ii) −x−1/2, −y+1, z−1/2; (iii) x−1/2, −y+3/2, −z+1; (iv) −x, y+1/2, −z+3/2; (v) x−1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C10H19N3O4 |
Mr | 245.28 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 173 |
a, b, c (Å) | 5.391 (5), 11.742 (10), 19.975 (16) |
V (Å3) | 1264.4 (19) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.48 × 0.18 × 0.08 |
Data collection | |
Diffractometer | Rigaku Mercury CCD area-detecter |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9374, 2887, 2200 |
Rint | 0.070 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.087, 0.96 |
No. of reflections | 2887 |
No. of parameters | 176 |
No. of restraints | 3 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.14, −0.17 |
Computer programs: CrystalClear (Rigaku, 2006), SHELXS97 (Sheldrick, 2008), Mercury (Macrae et al., 2006), SHELXL97 (Sheldrick, 2008) and Yadokari-XG 2009 (Kabuto et al., 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O3i | 0.97 (3) | 1.78 (3) | 2.743 (2) | 168 (2) |
N1—H2···O4ii | 0.92 (2) | 1.94 (2) | 2.822 (2) | 160 (2) |
N1—H2···O3ii | 0.92 (2) | 2.52 (2) | 3.260 (2) | 138 (2) |
N1—H3···O1iii | 0.89 (2) | 2.45 (2) | 3.031 (2) | 123 (2) |
N1—H3···O3iv | 0.89 (2) | 2.05 (2) | 2.870 (2) | 151 (2) |
N2—H5···O2v | 0.83 (2) | 2.05 (2) | 2.832 (2) | 155 (2) |
C1—H4···O1v | 1.00 | 2.33 | 3.269 (2) | 155 |
Symmetry codes: (i) −x+1/2, −y+1, z−1/2; (ii) −x−1/2, −y+1, z−1/2; (iii) x−1/2, −y+3/2, −z+1; (iv) −x, y+1/2, −z+3/2; (v) x−1, y, z. |
Acknowledgements
This work was partially supported by the JSPS KAKENHI (grant Nos. 24659548 and 23540478) and MEXT KAKENHI (grant No. 23108003).
References
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A moderately large number of oligopeptides are biologically active, and their structures are investigated to facilitate the determination of the possible conformations of oligopeptide and polypeptide chains. The N-terminus and C-terminus of L-leucylglycylglycine (L-LGG) are protonated and ionized, respectively, and the molecule is a zwitterion (Fig. 1). The main chain is in a folded form. The torsion angles of C2—N2—C3—C4 and N2—C3—C4—N3 are -87.54 (18)° and -52.78 (19)°, respectively. The N-terminal –NH3+ groups and the C-terminal –COO- groups form hydrogen bond networks (Fig. 2 & Fig. 3). One of the hydrogen atoms of the –NH3 group forms a three-centered hydrogen bond with the carboxyl and carboxyl oxygen atoms. In addition, intermolecular hydrogen bonds among amide groups (NH···O═C) are formed along the a axis. The hydrophobic region composed of leucyl side chains is surrounded by hydrophilic parts, and forms a column along the a axis.
In the case of the L-leucylglycylglycylglycine (Srikrishnan & Parthasarathy, 1987), the main chain is a folded form, and hydrophobic columns are formed along the a axis as in the case of L-LGG. On the other hand, the main chain of D,L-leucylglycylglycine (D,L-LGG) (Goswami et al., 1977) is in a nearly all-trans form expect the N-terminus. The main chains align parallel to the b axis in a head-to-tail manner and a β-sheetlike structure is formed parallel to the bc plane. The hydrophobic regions of the leucyl side chains and the hydrophilic regions are aligned alternately along the a axis. As in the case of D,L-LGG, the main chain in L-leucylglycine 0.67 hydrate (Kiyotani & Sugawara, 2012) is in a extended form, and hydrophobic and hydrophilic regions are aligned alternately along the c axis.