1.Direct radiation effects to the amino acid side chain: EMR and periodic DFT of X-irradiated L-asparagine at 6 K.
Øyen LF1, Aalbergsjø SG, Knudtsen IS, Hole EO, Sagstuen E. J Phys Chem B. 2015 Jan 15;119(2):491-502. doi: 10.1021/jp5115866. Epub 2015 Jan 6.
Radical formation in single crystals of L-asparagine monohydrate following X-irradiation at 6 K has been investigated at 6 K and at elevated temperatures using various electron magnetic resonance (EMR) techniques such as electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and ENDOR-induced EPR (EIE) spectroscopy. Molecular structures of the three free radicals stable at 6 K were assessed by detailed analysis of the experimental data and density functional theory (DFT) calculations in a periodic approach. Radical LI is assumed to result from one-electron reduction at the amide functional group in the asparagine side chain followed by protonation at the amide carbonyl oxygen by proton transfer from a neighboring molecule across a hydrogen bond. Radical LII is assigned to a one-electron reduction of the carboxyl group in the amino acid backbone, followed by proton transfer across a hydrogen bond between a carboxylic oxygen and a neighboring asparagine molecule.
2.Enzyme-assisted physicochemical enantioseparation processes-Part III: Overcoming yield limitations by dynamic kinetic resolution of asparagine via preferential crystallization and enzymatic racemiza
Würges K1, Petrusevska-Seebach K, Elsner MP, Lütz S. Biotechnol Bioeng. 2009 Dec 15;104(6):1235-9. doi: 10.1002/bit.22498.
The application of enantioseparation methods alone can only yield up to 50% of the desired chiral product. Thus enantioseparation becomes more attractive when accompanied by the racemization of the counter-enantiomer. Here we present first results of dynamic kinetic resolution of L-asparagine (L-Asn) via preferential crystallization and enzymatic racemization from a racemic, supersaturated solution on a 20 mL scale. An enzyme lyophilisate (WT amino acid racemase from P. putida KT2440 (E.C. 5.1.1.10), overexpressed in E. coli BL21(DE3)) was used for in situ racemization (enzyme concentrations varying from 0 to 1 mg/mL). When preferential crystallization was applied without any enzyme, a total of 31 mg of L-Asn monohydrate could be crystallized, before crystal formation of d-Asn started. Crystallization experiments accompanied by enzymatic racemization led to a significant increase of crystallized L-Asn (198 mg L-Asn monohydrate; >92%ee) giving the first experimental proof for this new process concept of dynamic kinetic resolution via preferential crystallization and enzymatic racemization.
3.Assessment on third order non linearity and other optical analyses of L-Asparagine Monohydrate single crystal: An efficient candidate for har
Thukral K1, Vijayan N2, Haranath D3, Jayaramakrishnan V4, Philip J5, Sreekanth P6, Bhagavannaryana G3. Spectrochim Acta A Mol Biomol Spectrosc. 2015 Dec 5;151:419-25. doi: 10.1016/j.saa.2015.05.051. Epub 2015 Jun 17.
Single crystal of l-Asparagine Monohydrate, an organic material has been successfully grown by slow evaporation solution growth technique at ambient condition. The lattice parameters and its strain of the grown crystal have been evaluated from powder X-ray diffraction and found that it belongs to orthorhombic crystal system. The polarizability has been measured by using the Clausius-Mossotti relation. The crystalline perfection of grown single crystal has been examined by high resolution X-ray diffraction and its imperfection in the diffraction plane was clearly visible by recording topographical image of the plane. From the high resolution XRD, it confirms that the crystal contained high crystalline perfection. The optical behavior was analyzed by photoluminescence and birefringence methods. In the photoluminescence, a broad peak has been observed at 475 nm which suggest that it emits blue light. The decay tendency of the material has also been observed by calculating decay constant.
4.A dual approach to study the electro-optical properties of a noncentrosymmetric L-asparagine monohydrate.
Shkir M1, Muhammad S2, AlFaify S2, Irfan A3, Yahia IS2. Spectrochim Acta A Mol Biomol Spectrosc. 2015 Feb 25;137:432-41. doi: 10.1016/j.saa.2014.08.033. Epub 2014 Aug 30.
In this work we reports the experimental and theoretical investigation on an organic noncentrosymmetric monohydrated L-asparagine (LAM) molecule. LAM single crystals were grown in specially designed beaker for the first time. Structural confirmation was done by identifying the vibrational modes using IR and FT-Raman spectroscopic studies. The ultra violet-visible-near infrared absorbance, diffuse reflectance spectra were recorded in the spectral range 190-2500 nm. The optical transparency was calculated and found to be ∼80%. Its optical band gap was calculated found to be ∼5.100 eV. Density functional theory (DFT) was employed to optimize the molecular geometry of LAM using B3LYP/6-31G(∗) basis set of theory. The HOMO-LUMO energy gap of 6.047 eV and transition energy of 176 nm (f0=0.024) have been found in semi-quantitative agreement with our experimental results. The dipole moment, polarizability and first hyperpolarizability were calculated at the same level of theory.
