Improved Signal-to-Background Ratio in Small-Angle X-ray Scattering Experiments with Synchrotron Radiation using an Evacuated Cell for Solutions

Abstract

An evacuated, temperature-controlled cell has been built for use on the small-angle X-ray scattering instrument D24 at the synchrotron radiation facility LURE. The sample is placed in a quartz capillary sealed in a stainless-steel holder using a vacuum-tight glue. Several O rings provide a vacuum path upstream and downstream from the cell, so that the X-ray beam only meets the capillary walls and the solution under study between the slits and the beam stop, while the sample is maintained under atmospheric pressure. The cell temperature is controlled via a water circulation through a copper sheath in tight contact with the steel holder. The use of this cell results in a marked reduction of the background, as observed in two series of parallel experiments using a conventional cell and this evacuated cell. The decrease ranges from a factor of 2 at s 1 values larger than 0.008 A,-to more than 15 at s --0.00116A -1, where s is the modulus of the scattering vector (s = 2sin 0/A, 20 is the scattering angle and A is the wavelength of the X-rays).

Everything SAXS: small-angle scattering pattern collection and correction

“…One type of instrument ends the in-vacuum collimation section with an x-ray transparent window, allowing for an in-air sample placement and environment before entering another x-ray transparent window delimiting the vacuum section to the detector (this sample-to-detector vacuum section is also known as the 'flight tube'). As this introduction of two x-ray transparent windows and an air path generates a non-negligible amount of small-angle scattering background, it does not lend itself well to samples with low scattering power [43]. The second instrument variant, therefore, consists of a vacuum sample chamber (and often a vacuum valve which can be closed to maintain the vacuum in the flight tube during the sample change procedure), and thus allows an uninterrupted flightpath from collimation through the sample into the flight tube.…”

Direct observation in solution of a preexisting structural equilibrium for a mutant of the allosteric aspartate transcarbamoylase

“…X-ray scattering curves were recorded on the small-angle scattering instrument D24 by using synchrotron radiation at Laboratoire pour l'Utilisation du Rayonnement Electromagnétique (LURE), Orsay, France. The instrument, the data acquisition system (40), the evacuated measuring cell (41), and the experimental procedures (23) have already been described. Data were recorded over the angular range 0.01 Å Ϫ1 Ͻ s Ͻ 0.05 Å Ϫ1 , where s ϭ (2sin )/ is the modulus of the scattering vector, 2 is the scattering angle, is the radiation wavelength ( ϭ 1.488 Å, absorption K-edge of Ni).…”

Structural Stability of Soybean Lipoxygenase-1 in Solution as Probed by Small Angle X-ray Scattering

“…The instrument, the data acquisition system and the evacuated measuring cell have been described. 39 In the course of several measuring sessions, samples from two different preparations were used. Freshly prepared samples of LOX-1 were measured at two different concentrations in the buffer used in the final step of purification.…”

“…For this purpose, the following protein samples were used: native calpain from human erythrocytes (110 kDa, 1.3 mg/ml) in 50 mM sodium borate (pH 7.5) containing 0.1 mM EDTA; 16S and CaeSS2 Hc from C. aestuarii (450 kDa, 1.5 mg/ml and 75 kDa, 1.2 mg/ml, respectively) in 50 mM Tris-HCl (pH 7.0), 20 mM CaCl 2 . 39 The distance distribution function, representing the distribution of distances between any pair of volume elements within the particle, together with the structural parameters derived from p(r), i.e. the maximum dimension of the particle (D max ), and the radius of gyration, were evaluated using the indirect transform method as implemented in the program GNOM.…”