Search

With the recent atomic models for the sarcoplasmic reticulum Ca2+-ATPase in the Ca2+-bound state, the Ca2+-free, thapsigargin-inhibited state, and the Ca2+-free, vanadate-inhibited state, we are that much closer to understanding and animating the Ca2+-transport cycle. These „snapshots” of the Ca2+-transport cycle reveal an impressive breadth and complexity of conformational change. The cytoplasmic domains undergo rigid-body movements that couple the energy of ATP to the transport of Ca2+ across the membrane. Large-scale rearrangements in the transmembrane domain suggest that the Ca2+-binding sites may alternately cease to exist and reform during the transport cycle. Of the three cytoplasmic domains, the actuator (A) domain undergoes the largest movement, namely a 110° rotation normal to the membrane. This domain is linked to transmembrane segments M1–M3, which undergo large rearrangements in the membrane domain. Together, these movements are a main event in Ca2+ transport, yet their significance is poorly understood. Nonetheless, inhibition or modulation of Ca2+-ATPase activity appears to target these conformational changes. Thapsigargin is a high-affinity inhibitor that binds to the M3 helix near Phe256, and phospholamban is a modulator of Ca2+-ATPase activity that has been cross-linked to M2 and M4. The purpose of this review is to postulate roles for the A domain and M1–M3 in Ca2+ transport and inhibition. [ABSTRACT FROM AUTHOR]

A new optical data storage technology based on the surface-enhanced Raman scattering (SERS) effect has been developed for high-density optical memory and three-dimensional data storage. With the surface-enhanced Raman optical data storage (SERODS) technology, the molecular interactions between the optical layer molecules and the substrate are modified by the writing laser, changing their SERS properties, so that they are encoded to store information as bits. Since the SERS properties are extremely sensitive to molecular microenvironments, very small "spectrochemical holes" approaching the diffraction limit can be produced for the writing process. The SERODS device uses a reading laser to induce the SERS emission of molecules on the disk and a photometric detector tuned to the frequency of the Raman spectrum to retrieve the stored information. The results illustrate that SERODS is capable of three-dimensional data storage. [ABSTRACT FROM AUTHOR]