A fast and portable microspectrophotometer for protein crystallography

1993 ◽  
Vol 26 (6) ◽  
pp. 839-842 ◽  
Author(s):  
A. Hadfield ◽  
J. Hajdu
Keyword(s):  
Structural Data ◽  
Array Detector ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
Near Ir ◽  
Photodiode Array Detector ◽  
Photodiode Array ◽  
The Right ◽  
Measurement Area

Spectroscopic measurements on crystals during X-ray data collection provide additional information on the composition of the crystal and can be used in the interpretation of structural data. This paper describes a portable microspectrophotometer to obtain UV–visible–near-IR spectra from single crystals during X-ray measurements. The instrument consists of a deuterium lamp, optical fibres, a pair of mirror lenses and a monochromator equipped with a photodiode array detector. Spectra can be recorded in short periods of time (a few milliseconds) from a measurement area of 0.10 mm diameter or smaller. The device can be used to monitor spectral changes in crystals during time-resolved X-ray experiments so that the X-ray camera can be triggered at the right moment as determined by the spectrum, thereby eliminating much of the present guesswork from such studies.

Differentiation Between Sulfoaildenafil and Its Analogs

2011 ◽  
Vol 94 (6) ◽  
pp. 1770-1777 ◽  
Author(s):  
Takako Moriyasu ◽  
Keiko Minowa ◽  
Miho Sakamoto ◽  
Kiyoko Kishimoto ◽  
Hideo Kadoi ◽  
...  
Keyword(s):  
Mass Spectra ◽  
Ion Trap ◽  
Selective Inhibitor ◽  
Array Detector ◽  
X Ray ◽  
Nmr Spectrometry ◽  
Photodiode Array Detector ◽  
Photodiode Array ◽  
The Relationship ◽  
Phosphodiesterase 5

Abstract An analog of aildenafil, which is a potent and highly selective inhibitor of phosphodiesterase 5, was found in a dietary supplement marketed for enhancement of sexual function. The compound was isolated by silica gel column chromatography, and its structure was identified by means of 13C-NMR spectrometry, 1H-NMR spectrometry, high-resolution MS, and X-ray structure determination. The compound was identified to be sulfoaildenafil (other names: thioaildenafil, dimethyl sildenafil thione, and thiomethisosildenafil). Sulfoaildenafil is very similar to the compound thiohomosildenafil. As it is difficult to distinguish between them by LC-photodiode array detector analysis, ultra-performance LC (UPLC)/MS, ion trap LC/MS/MS (LC/IT-MS/MS), and GC/MS were performed. The mass spectra of thiohomosildenafil by UPLC/MS and LC/IT-MS/MS showed mass fragments of m/z 58, 72, and 355, and the mass spectrum by GC/MS showed mass fragments of m/z 56, 72, and 420. Some of these fragments had low intensities, but they were useful for distinguishing between the two compounds. The relationship between aildenafil (other names: dimethylsildenafil and methisosildenafil) and homosildenafil is similar to that between sulfoaildenafil and thiohomosildenafil. Therefore, these were also examined.

Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

1983 ◽  
Vol 41 ◽  
pp. 766-767
Author(s):  
Eva-Maria Mandelkow ◽  
Eckhard Mandelkow ◽  
Joan Bordas
Keyword(s):  
Electron Microscopy ◽  
Dynamic Equilibrium ◽  
Time Resolved ◽  
X Ray ◽  
Additional Information ◽  
X Ray Scattering ◽  
Low Concentrations ◽  
Microtubule Growth ◽  
Ray Patterns ◽  
Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

Determination of Niacin in Infant Formula by Solid-phase Clean-up and HPLC with Photodiode Array Detector

2009 ◽  
Vol 38 (3) ◽  
pp. 359-363
Author(s):  
Jee-Eun Hong ◽  
Mi-Ran Kim ◽  
Sang-Hee Cheon ◽  
Jung-Young Chai ◽  
Eun-Ryong Park ◽  
...  
Keyword(s):  
Infant Formula ◽  
Solid Phase ◽  
Array Detector ◽  
Photodiode Array Detector ◽  
Photodiode Array

Development and Validation of an HPLC Method for Determination of Spirotetramat and Spirotetramat cis enol in Various Vegetables and Soil

2013 ◽  
Vol 96 (3) ◽  
pp. 670-675 ◽  
Author(s):  
Balwinder Singh ◽  
Kousik Mandal ◽  
Sanjay K Sahoo ◽  
Urvashi Bhardwaj ◽  
Raminderjit Singh Battu
Keyword(s):  
Analytical Method ◽  
Anhydrous Sodium Sulfate ◽  
Hplc Method ◽  
Array Detector ◽  
Photodiode Array Detector ◽  
Photodiode Array ◽  
Precision And Accuracy ◽  
Hplc Grade Acetonitrile ◽  
Development And Validation

Abstract An easy and simple analytical method was standardized and validated for the estimation of residues of spirotetramat and its metabolite spirotetramat cis enol in various substrates: okra fruits, brinjal leaves and fruits, green chili, red chili, and soil. The samples were extracted with acetonitrile, diluted with brine solution, partitioned into dichloromethane, dried over anhydrous sodium sulfate, and cleaned up by treatment with activated charcoal powder. Final clear extracts were concentrated under vacuum and reconstituted with HPLC grade acetonitrile. Residues were estimated using HPLC with a photodiode array detector and a C18 column, and confirmed by HPTLC. Acetonitrile was used as the mobile phase at 0.4 mL/min. Both spirotetramat and spirotetramat cis enol presented distinct peak at retention times of 8.518 and 7.598 min, respectively. Consistent recoveries ranging from 82 to 97% for spirotetramat and spirotetramat cis enol were observed when samples were spiked at 1.00 to 0.03 mg/kg levels. The LOQ of the method was found to be 0.03 mg/kg. The analytical method was validated in terms of parameters, including selectivity, linearity, precision, and accuracy.

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