Chirality Inversion Process of a Bulky Alkyl Group in the Crystalline State Photo‐Isomerization of Cobaloxime Complex Crystals

2013 ◽  
Vol 60 (7) ◽  
pp. 898-906 ◽  
Author(s):  
Hiraku Takeoka ◽  
Akiko Sekine ◽  
Hidehiro Uekusa ◽  
Yuji Ohashi
Keyword(s):  
Alkyl Group ◽  
Crystalline State ◽  
Inversion Process ◽  
Complex Crystals

scholarly journals Control of Photochromism in Crystalline-State in Dual Photoisomeric Complexes

2014 ◽  
Vol 70 (a1) ◽  
pp. C920-C920
Author(s):  
Akiko Sekine ◽  
Yuta Yamazaki ◽  
Kohei Johmoto ◽  
Hidehiro Uekusa
Keyword(s):  
Visible Light ◽  
Alkyl Group ◽  
Crystalline State ◽  
Structural Changes ◽  
Dynamic Control ◽  
Crystal Form ◽  
Photochromic Property ◽  
In Situ Control ◽  
Photochromic Materials

Photochromic materials have attracted attention in recent years, however, in situ control of the photochromic reactivities still challenging. In order to realize dynamic control of photochromic property in crystal, we designed and created new dual photoisomeric type cobaloxime complexes, in which the reactivity of photochromic ligand changes by contact with surrounding photoreactive ligands. In this study, salicylideneaniline derivatives (SAP) are used as photochromic ligands, and the relationships between their photochromic reactivity and structural changes induced by crystalline-state photoisomerization of alkyl group of cobaloxime complex were investigated. As a salicylideneaniline (SAP) type cobaloxime complex, (3-cyanopropyl)(N-(3,5-di-tert-butylsalicylidene)-3-aminopyridine)cobaloxime was successfully synthesized. In the crystal, the SAP moiety which had a twisted conformation (dihedral angle of rings, 30.0(6)0)showed the photochromism upon UV irradiation. Also the 3-1 photoisomerization of the 3-cyanopropyl group in the cobaloxime moiety occurred with retention of the single-crystal form upon visible light irradiation. After crystalline-state 3-1 photoisomerization of the alkyl group by visible light, the photochromic property was examined to show the lifetime of colored species became significantly longer than before the reaction. It would be explained that the reaction cavity around the SAP moiety was modified by solid-state photoisomerization of alkyl group of the surrounding cobaloxime complexes, which successfully enabled the control of the photochromism. Moreover, other several derivatives are investigated similarly and their results were discussed together.

scholarly journals Chirality inversion process in cobaloxime complex crystals by photoirradiation

2005 ◽  
Vol 61 (a1) ◽  
pp. c313-c313
Author(s):  
A. Sekine ◽  
T. Nitami ◽  
K. Sasaki ◽  
H. Takeoka ◽  
H. Uekusa ◽  
...  
Keyword(s):  
Inversion Process ◽  
Complex Crystals

Merging of electron-diffraction intensities acquired with a slow-scan CCD camera of crotoxin complex crystals to 3.5Å resolution

1994 ◽  
Vol 52 ◽  
pp. 104-105
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Electron Diffraction ◽  
Ccd Camera ◽  
Crystal Thickness ◽  
Local Contrast ◽  
Camera Model ◽  
Data Set ◽  
3 Dimensional ◽  
Diffraction Mode ◽  
Diffraction Patterns ◽  
Complex Crystals

Crotoxin complex is the principal neurotoxin of the South American rattlesnake, Crotalus durissus terrificus and has a molecular weight of 24 kDa. The protein is a heterodimer with subunit A assigneda chaperone function. Subunit B carries the lethal activity, which is exerted on both sides ofthe neuro-muscular junction, and which is thought to involve binding to the acetylcholine receptor. Insight in crotoxin complex’ mode of action can be gained from a 3 Å resolution structure obtained by electron crystallography. This abstract communicates our progress in merging the electron diffraction amplitudes into a 3-dimensional (3D) intensity data set close to completion. Since the thickness of crotoxin complex crystals varies from one crystal to the other, we chose to collect tilt series of electron diffraction patterns after determining their thickness. Furthermore, by making use of the symmetry present in these tilt data, intensities collected only from similar crystals will be merged.Suitable crystals of glucose-embedded crotoxin complex were searched for in the defocussed diffraction mode with the goniometer tilted to 55° of higher in a JEOL4000 electron cryo-microscopc operated at 400 kV with the crystals kept at -120°C in a Gatan 626 cryo-holder. The crystal thickness was measured using the local contrast of the crystal relative to the supporting film from search-mode images acquired using a 1024 x 1024 slow-scan CCD camera (model 679, Gatan Inc.).

Cryomicroscopy of crotoxin complex crystals at 400 KV

1989 ◽  
Vol 47 ◽  
pp. 826-827
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Signal To Noise Ratio ◽  
3D Structure ◽  
Three Dimensional ◽  
Carbon Films ◽  
Depth Of Field ◽  
Basic Subunit ◽  
Ewald Sphere ◽  
Diffraction Patterns ◽  
Complex Crystals ◽  
Acidic Subunit

The crotoxin complex is a potent neurotoxin composed of a basic subunit (Mr = 12,000) and an acidic subunit (M = 10,000). The basic subunit possesses phospholipase activity whereas the acidic subunit shows no enzymatic activity at all. The complex's toxocity is expressed both pre- and post-synaptically. The crotoxin complex forms thin crystals suitable for electron crystallography. The crystals diffract up to 0.16 nm in the microscope, whereas images show reflections out to 0.39 nm2. Ultimate goal in this study is to obtain a three-dimensional (3D-) structure map of the protein around 0.3 nm resolution. Use of 100 keV electrons in this is limited; the unit cell's height c of 25.6 nm causes problems associated with multiple scattering, radiation damage, limited depth of field and a more pronounced Ewald sphere curvature. In general, they lead to projections of the unit cell, which at the desired resolution, cannot be interpreted following the weak-phase approximation. Circumventing this problem is possible through the use of 400 keV electrons. Although the overall contrast is lowered due to a smaller scattering cross-section, the signal-to-noise ratio of especially higher order reflections will improve due to a smaller contribution of inelastic scattering. We report here our preliminary results demonstrating the feasability of the data collection procedure at 400 kV.Crystals of crotoxin complex were prepared on carbon-covered holey-carbon films, quench frozen in liquid ethane, inserted into a Gatan 626 holder, transferred into a JEOL 4000EX electron microscope equipped with a pair of anticontaminators operating at −184°C and examined under low-dose conditions. Selected area electron diffraction patterns (EDP's) and images of the crystals were recorded at 400 kV and −167°C with dose levels of 5 and 9.5 electrons/Å, respectively.

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