Charge density study of N-acetyl-L-tyrosine ethyl ester monohydrate derived from CCD area detector data

The crystal structure, thermal vibrations and electron density of the peptide N-acetyl-L-tyrosine ethyl ester monohydrate, C13H17NO4. H2O, have been analysed using single-crystal X-ray diffraction data collected at 110K with Mo K alpha radiation to a resolution of (sin theta/lambda)(max) = 1.1 Angstrom(-1). A CCD area detector was used to collect 98 393 data during one week. A multipolar atom density model was fitted against the 10 189 unique data with I > 2 sigma(I) [R(F) = 0.027, wR(F) = 0.020, g.o.f. = 0.65] in order to map the valence electron distribution. These deformation densities compare very well with those obtained from conventional diffractometers equipped with scintillation detectors. This work shows that area detectors permit charge density studies in a more routine way than is possible with conventional diffractometers.