Browsing by Author "Nakabayashi, Seiichiro"

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Growth Promotion of Targeted Crystal Face by Nanoprocessing via Laser Ablation
(2019-10-10)
Wu, Chi-Shiun
;
Ikeyama, Jun
;
Nakabayashi, Seiichiro
;
Sugiyama, Teruki
;
Yoshikawa, Hiroshi Y.
Control of crystal shape is an indispensable step for various applications of crystalline products. However, obtaining the desired crystal shape by conventionally tuning environmental conditions (temperature, additives, etc.) cannot always be reached. Recently, we have developed an innovative approach for spatiotemporal control of crystal growth of proteins and amino acids by locally modifying crystal structure (e.g., formation of screw dislocations) via femtosecond (fs) laser ablation. In this work, to clarify the appropriate laser condition for controlling the shape of single crystals with minimized damage, we first systematically investigated the dependence of pulse duration on laser ablation and crystal growth of L-phenylalanine (L-Phe). By using a laser system with tunable pulse durations from fs to nanoseconds (ns), we found fs laser ablation can offer nanometer-sized, sharp etching of which diameter was smaller than the diffraction limit. By utilizing such nanoprocessing via fs laser ablation for promoting the growth of a targeted crystal face, we successfully demonstrated the preparation of a bulky crystal of L-Phe, which is difficult to be obtained by conventional crystallization methods.
Spatially Precise, Soft Microseeding of Single Protein Crystals by Femtosecond Laser Ablation
(2012-09-01)
Yoshikawa, Hiroshi Y.
;
Hosokawa, Yoichiroh
;
Murai, Ryota
;
Sazaki, Gen
;
Kitatani, Tomoya
We developed a spatially precise, soft microseeding method for the production of single protein crystals that are suitable for X-ray crystallographic studies. We used focused femtosecond laser pulses to produce, via multiphoton absorption processes, seed crystals from small regions (similar to 1 mu m(2)) of crystals. Hen egg-white lysozyme seed crystals, produced in this manner, grew to be single crystals without any deterioration in their crystallinity. We also validated the technique using polycrystals for the membrane protein, acriflavine resistance protein B, for which single crystals are very difficult to obtain. In addition, we found that the shape of a tetragonal lysozyme crystal prepared from the seed could be controlled by altering the time interval between the initiation of crystallization and laser ablation. We also tried to comprehend the mechanism of femtosecond laser-induced microseeding. We visualized the ablated surfaces of the lysozyme crystals by atomic force microscopy and by laser confocal microscopy combined with differential interference microscopy. The results obtained in this study clearly demonstrate that femtosecond laser ablation of protein crystals is based on a photomechanical process, which ejects crystal fragments with little thermal damage. Femtosecond laser ablation is indeed very promising to produce high quality protein seed crystals from polycrystals or cracked crystals that are not suitable for X-ray diffraction studies.