Optical design and performance of the biological small-angle X-ray scattering beamline at the Taiwan Photon Source.

The optical design and performance of the recently opened 13A biological small-angle X-ray scattering (SAXS) beamline at the 3.0 GeV Taiwan Photon Source of the National Synchrotron Radiation Research Center are reported. The beamline is designed for studies of biological structures and kinetics in a wide range of length and time scales, from angstrom to micrometre and from microsecond to minutes. A 4 m IU24 undulator of the beamline provides high-flux X-rays in the energy range 4.0-23.0 keV. MoB4C double-multilayer and Si(111) double-crystal monochromators (DMM/DCM) are combined on the same rotating platform for a smooth rotation transition from a high-flux beam of ∼4 × 1014 photons s-1 to a high-energy-resolution beam of ΔE/E ≃ 1.5 × 10-4; both modes share a constant beam exit. With a set of Kirkpatrick-Baez (KB) mirrors, the X-ray beam is focused to the farthest SAXS detector position, 52 m from the source. A downstream four-bounce crystal collimator, comprising two sets of Si(311) double crystals arranged in a dispersive configuration, optionally collimate the DCM (vertically diffracted) beam in the horizontal direction for ultra-SAXS with a minimum scattering vector q down to 0.0004 Å-1, which allows resolving ordered d-spacing up to 1 µm. A microbeam, of 10-50 µm beam size, is tailored by a combined set of high-heat-load slits followed by micrometre-precision slits situated at the front-end 15.5 m position. The second set of KB mirrors then focus the beam to the 40 m sample position, with a demagnification ratio of ∼1.5. A detecting system comprising two in-vacuum X-ray pixel detectors is installed to perform synchronized small- and wide-angle X-ray scattering data collections. The observed beamline performance proves the feasibility of having compound features of high flux, microbeam and ultra-SAXS in one beamline.

Antibiotic activity of lectins from marine algae against marine vibrios.

Saline and aqueous ethanol extracts of marine algae and the lectins from two red algal species were assayed for their antibiotic activity against marine vibrios. Experimental studies were also carried out on the influence of environmental factors on such activity, using batch cultures. The results indicated that many of the saline extracts of the algal species were active and that the activity was selective against those vibrios assayed. The algal extracts were active against Vibrio pelagius and the fish pathogen V. vulnificus, but inactive against V. neresis. Algal lectins from Eucheuma serra (ESA) and Galaxaura marginata (GMA) strongly inhibited V. vulnificus but were inactive against the other two vibrios. The antibacterial activity of algal extracts was inhibited by pretreatment with various sugars and glycoprotein. Extracts of the two red algae, E. serra and Pterocladia capillacea, in saline and aqueous ethanol, inhibited markedly the growth rate of V. vulnificus at very low concentrations. Culture results indicated that metabolites active against V. vulnificus were invariably produced in P. capillacea over a wide range of temperature, light intensity, and nutritional conditions. Enhanced antibacterial activity occurred when P. capillacea was grown under higher irradiance, severe nutrient stress and moderate temperature (20 degrees C), reflecting the specific antibiotic characteristics of this alga. The strong antibiotic activity of lectins towards fish pathogenic bacteria reveals one of the important roles played by algal lectins, as well as the potential high economic value of those marine algae assayed for aquaculture and for biomedical purposes.