Acid-free paper Acid-free paper Acid-free paper is paper that if infused in water yields a neutral or basic pH (7 or slightly greater). It can be made from any cellulose fiber as long as the active acid pulp is eliminated during processing. It is also lignin- and sulfur-free. Acid-free paper addresses the problem of preserving documents and artwork for long periods. Paper made from wood-based pulp that has not had its lignin removed turns yellow, becomes brittle, and deteriorates over time. When exposed to light and/or heat, the molecules in the acidic paper will break down even faster. Acidic wood-pulp paper became
6TMS neutral amino acid transporter family multidrug efflux pump of the RND superfamily (TC #2.A.6.2)) and the "mar" regulon itself, and (3) MarB, a small protein of 71 amino acyl residues of unknown function. A periplasmic binding protein, MppA, essential for the uptake of the cell wall murein tripeptide, L-alanyl-γ-D-glutamyl-"meso"-diaminopimelate via the Opp permease, regulates "mar" regulon expression. Loss of MppA causes overproduction of MarA which activates "acrAB", causing pleiotropic drug resistance. MppA probably functions upstream of MarA in a signal transduction pathway that negatively controls expression of the "marRAB" operon. 6TMS neutral amino acid transporter family The 6TMS Neutral Amino Acid Transporter (NAAT) Family (TC#