The lipid–teichoic acid complex in the cytoplasmic membrane of Streptococcus faecalis N.C.I.B. 8191

1. A lipid–teichoic acid complex was isolated from Streptococcus faecalis N.C.I.B. 8191. The covalent nature of the linkage between teichoic acid and lipid was established. 2. The complex exhibits macromolecular properties in solution, and ultracentrifugation studies show that these are due to micelle formation. 3. From chemical studies it is concluded that the teichoic acid is a poly(glycerol phosphate) in which some of the glycerol hydroxyl groups possess kojibiosyl [2-O-α-d-glucopyranosyl-(1→2)-α-d- glucopyranosyl] substituents, together with d-alanine ester residues. 4. The lipid is 1-kojibiosyl diglyceride, already known as a membrane component of this organism, with probably a phosphatidyl substituent. The phosphatidyl kojibiosyl diglyceride is attached to the teichoic acid through a phosphodiester linkage, and the chain of the teichoic acid contains 28–35 units. 5. Although the complex represents the whole of the membrane teichoic acid in this organism, only about 12% of the membrane glycolipid is associated with teichoic acid. 6. Two phosphatidyl glycolipids, closely resembling that bearing the teichoic acid, were isolated from the lipids of the organism and were partly characterized

A Sticker Based Model for DNA Computation

We introduce a new model of molecular computation that we call the sticker model. Like many previous proposals it makes use of DNA strands as the physical substrate in which information is represented and of separation by hybridization as a central mechanism. However, unlike previous models, the stickers model has a random access memory that requires no strand extension, uses no enzymes, and (at least in theory) its materials are reusable. The paper describes computation under the stickers model and discusses possible means for physically implementing each operation. We go on to propose a specific machine architecture for implementing the stickers model as a microprocessor-controlled parallel robotic workstation. Finally, we discuss several methods for achieving acceptable overall error rates for a computation using basic operations that are error prone. In the course of this development a number of previous general concerns about molecular computation [Smith, Hartmanis, Letters to Sci..