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- OrthoTec 2012
Jun 06-07, Winona Lake, IN, USA - ACHEMA 2012
Jun 18-22, Frankfurt/M., Germany - Seeing at the Nanoscale 2012
Jul 09-11, Bristol, UK - ACA Annual Meeting
Jul 28-Aug 01, Boston, Massachusettes, USA - ACS Fall
Aug 19-21, Philadelphia, Pennsylvania, USA
IμS with Copper Radiation – Absolute configuration from light atom structures
The IμS with Quazar optics delivers a 2D focused beam with an unprecedented flux of more than 5 x 109 X-rays/(s mm2). The excellent beam stability guarantees high data quality allowing absolute structure determination on very small samples with no atoms heavier than oxygen.
- Vitamin C
Absolute configuration of Vitamin C
Intensity data were collected on a small crystal of Vitamin C (40 μm x 100 μm x 100 μm) using an APEX II QUAZAR with Cu radiation. Data are 10 fold redundant and complete to 0.83 Å. The structure refines with a reliability criteria R1 of 2.25% a Flack x parameter of 0.03(15) and an Hooft y parameter of 0.04(16).
The determination of absolute configuration
Currently, the established method to determine the absolute configuration of a chiral molecule calls for the determination of the Flack x parameter. Flack, H.D. (1983). Acta Cryst. A39, 876-881. A new statistical method based on Bayesian statistics was developed by Rob Hooft et al. J. Appl. Cryst. (2008). 41, 96-103 and determines the Hooft y parameter.
It is possible to determine the absolute structure of chiral compounds by accurately measuring the small differences (Bijvoet anomalies) of Friedel pairs. Data have to be collected very carefully using highly performing instrumentation to allow the detection of these small differences in measured intensity data.
