(IUCr) Crystallography Journals Online checkcif report

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Acta Cryst. (2003). E59, o1581-o1583 [ doi:10.1107/S1600536803020889 ]

N-HO=C hydrogen bonding and OO=C repulsive interactions in tert-butoxycarbonyl-L-leucyl-L-alanine ethyl ester (Boc-L-Leu-L-Ala-OEt)

H. Oku, K. Yamada and R. Katakai

Online 30 September 2003

Key indicators

Single-crystal X-ray study
T = 173 K
Mean (C-C) = 0.008 Å
R factor = 0.067
wR factor = 0.159
Data-to-parameter ratio = 10.7

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT201_ALERT_2_A Isotropic non-H Atoms in Main Residue(s) ..... =         32

Author Response: Because of the limited numbers of observed reflections. Even at the low temperature condition (173 K), diffractions from the crystal of (I) were too weak to collect enough numbers. Therefore only main-cain atoms were refefined anisotropically.


Alert level B
PLAT220_ALERT_2_B Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       3.54 Ratio

Author Response: It is due to the difference of thermal mobility. The atoms located at chain-ends and amino-acid side chains often show higer U(eq) compared with the atoms located inside of the molecule.


Alert level C
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.60 Ratio

PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.91 Ratio

PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.55 Ratio

PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C211

Author Response: It is due to the difference of thermal mobility. The chain end atoms (C212, C213, and C214) often show higer U(eq) compared with the atoms (such as C211) located inside of the chain.

PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C224

PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C311

PLAT242_ALERT_2_C Check Low    U(eq) as Compared to Neighbors ....       C324

PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          8

Author Response: The chain end atoms (-OEt) often show lower bond precision due to their higher thermal mobility compared with the atoms located inside of the chain.

PLAT360_ALERT_2_C Short  C(sp3)-C(sp3) Bond  C341   -   C342     =       1.43 Ang.

Author Response: The short bond length is attributable to the to their higher thermal mobility compared with the atoms located inside of the chain.


Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           68.25
           From the CIF: _reflns_number_total               5906
           Count of symmetry unique reflns         5906
           Completeness (_total/calc)            100.00%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present           no

Author Response: The absolute stereochemistry was not established from the diffraction experiment. All the Friedel pairs are averaged. The absolute configuration was confirmed from the analytical data. The explanation has been added into the text.


   1 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   9 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   9 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion