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The structure based drug design has been limited by various factors that include protein crystallization, which is one of the most challenging tasks in this area. It has been proved unequivocally that X-ray crystallography is highly trusted technique for three dimensional structure determination of small-and macro-molecules. It has provided the definite solution for several key areas such as structure based drug design, site directed mutagenesis and elucidation of enzyme mechanisms. In X-ray crystallography, growing good quality of crystals for structure determination is always, the rate limiting step. Various approaches including laser induced crystallization technique has been reported to tackle this issue. We report on the crystallization of small-and macro-molecules under focused optical radiation from a femtosecond laser (λ = 800 nm). The efficacy of this technique is proved by crystallizing different samples such as sodium chloride and urea, and by comparing the results to those crystals obtained by conventional methods. In addition, the unique capability of the developed technique is demonstrated by crystallizing the three chalcone compounds that are difficult to crystallize using conventional methods. Furthermore, the developed technique is extended to crystallize protein molecule (lysozyme) and the results indicate that present technique is a potential alternative tool to crystallize biomolecules.

Optical traps (tweezers) are beginning to be used with increasing efficacy in diverse studies in the biological and biomedical sciences. We report here results of a systematic study aimed at enhancing the efficiency with which dielectric (transparent) materials can be optically trapped. Specifically, we investigate how truncation of the incident laser beam affects the strength of an optical trap in the presence of a circular aperture. Apertures of various sizes have been used by us to alter the beam radius, thereby changing the effective numerical aperture and intensity profile. We observe significant enhancement of the radial and axial trap stiffness when an aperture is used to truncate the beam compared to when no aperture was used, keeping incident laser power constant. Enhancement in trap stiffness persists even when the beam intensity profile is modulated. The possibility of applying truncation to multiple traps is explored; to this end a wire mesh is utilized to produce multiple trapping that also alters the effective numerical aperture. The use of a mesh leads to reduction in trap stiffness compared to the case when no wire mesh is used. Our findings lead to a simple-to-implement and inexpensive method of significantly enhancing optical trapping efficiency under a wide range of circumstances.

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