Decorin content and near infrared spectroscopy analysis of dried collagenous biomaterial samples.

The efficient removal of proteoglycans, such as decorin, from the hide when processing it to leather by traditional means is generally acceptable and beneficial for leather quality, especially for softness and flexibility. A patented waterless or acetone dehydration method that can generate a product similar to leather called Dried Collagenous Biomaterial (known as BCD) was developed but has no effect on decorin removal efficiency. The Alcian Blue colorimetric technique was used to assay the sulfated glycosaminoglycan (sGAG) portion of decorin. The corresponding residual decorin content was correlated to the mechanical properties of the BCD samples and was comparable to the control leather made traditionally. The waterless dehydration and instantaneous chrome tanning process is a good eco-friendly alternative to transforming hides to leather because no additional effects were observed after examination using NIR spectroscopy and additional chemometric analysis.

Fe(2+)-tetracycline-mediated cleavage of the Tn10 tetracycline efflux protein TetA reveals a substrate binding site near glutamine 225 in transmembrane helix 7.

TetA specified by Tn10 is a class B member of a group of related bacterial transport proteins of 12 transmembrane alpha helices that mediate resistance to the antibiotic tetracycline. A tetracycline-divalent metal cation complex is expelled from the cell in exchange for a entering proton. The site(s) where tetracycline binds to this export pump is not known. We found that, when chelated to tetracycline, Fe(2+) cleaved the backbone of TetA predominantly at a single position, glutamine 225 in transmembrane helix 7. The related class D TetA protein from plasmid RA1 was cut at exactly the same position. There was no cleavage with glycylcycline, an analog of tetracycline that does not bind to TetA. The Fe(2+)-tetracycline complex was not detectably transported by TetA. However, cleavage products of the same size as with Fe(2+) occurred with Co(2+), known to be cotransported with tetracycline. The known substrate Mg (2+)-tetracycline interfered with cleavage by Fe(2+). These findings suggest that cleavage results from binding at a substrate-specific site. Fe(2+) is known to be able to cleave amide bonds in proteins at distances up to approximately 12 A. We conclude that the alpha carbon of glutamine 225 is probably within 12 A of the position of the Fe(2+) ion in the Fe(2+)-tetracycline complex bound to the protein.