Crystallization of a human galectin-3 variant with two ordered segments in the shortened N-terminal tail

Among members of the family of adhesion/growth-regulatory galectins, galectin-3 (Gal-3) bears a unique modular architecture. A N-terminal tail (NT) consisting of the N-terminal segment (NTS) and nine collagen-like repeats is linked to the canonical lectin domain. In contrast to bivalent protoand tandem-repeat-type galectins, Gal-3 is monomeric in solution, capable to self-associate in the presence of bi-to multivalent ligands, and the NTS is involved in cellular compartmentalization. Since no crystallographic information on Gal-3 beyond the lectin domain is available, we used a shortened variant with NTS and repeats VII-IX. This protein crystallized as tetramers with contacts between the lectin domains. The region from Tyr101 (in repeat IX) to Leu114 (in the CRD) formed a hairpin. The NTS extends the canonical beta-sheet of F1-F5 strands with two new beta-strands on the F face. Together, crystallographic and SAXS data reveal a mode of intramolecular structure building involving the highly flexible Gal-3's NT

Saccharothrix sp. PAL54, a new chloramphenicol-producing strain isolated from a Saharan soil

An actinomycete strain designated PAL54, producing an antibacterial substance, was isolated from a Saharan soil in Ghardaïa, Algeria. Morphological and chemical studies indicated that this strain belonged to the genus Saccharothrix. Analysis of the 16S rDNA sequence showed a similarity level ranging between 96.9 and 99.2% within Saccharothrix species, with S. longispora DSM 43749T, the most closely related. DNA–DNA hybridization confirmed that strain PAL54 belonged to Saccharothrix longispora. It showed very strong activity against pathogenic Gram-positive and Gram-negative bacteria responsible for nosocomial infections and resistant to multiple antibiotics. Strain PAL54 secreted the antibiotic optimally during mid-stationary and decline phases of growth. One antibacterial compound was isolated from the culture broth and purified by HPLC. The active compound was elucidated by uv-visible and NMR spectroscopy and by mass spectrometry. The results showed that this compound was a D(-)-threo chloramphenicol. This is the first report of chloramphenicol production by a Saccharothrix species

Dipolar random field Ising model: an application to garnet films

The dipolar-random field Ising model (DRFIM) recently introduced displays a behaviour that can be connected to the magnetization of bidimensional magnetic media. Epitaxial magnetic garnet films seem to be the ideal test material for such a model. In this work the results of the measurements performed on garnet samples are presented, as well as the comparisons with simulation results obtained by the DRFIM. The results prove that a variety of hysteresis loops are well described by the DRFIM. This capability does not derive from the fine tuning of a great number of parameters, but by the interplay of exchange and dipolar interactions.Comment: HTML paper, GIF images. To appear on Phys.Rev.B (Brief Reports). Application of the model published on Phys.Rev.B 59 (1999) 985, cond-mat/990707

Hysteresis properties at zero temperature in the Dipolar-Random Field Ising Model

We present a modified two-dimensional random field Ising model, where a dipolar interaction term is added to the classic random field Hamiltonian. In a similar model it was already verified that the system state can exhibit domains in the form of stripe patterns, typical of thin materials with strong perpendicular anisotropy. In this work we show that the hysteresis loops obtained at zero temperature can display a strict similarity with the loops obtained in thin magnetic materials such as garnet films. In our model the processes of domain nucleation and domain wall motion are well separated in time as the system evolves. This remarkable fact allowed us to better understand the nucleation process in this family of spin systems.Comment: HTML paper, GIF images. Subsequent application of the model to appear on Phys.Rev.B (Brief Reports), and on cond-ma