Models for molecular computation: conformational automata in thecytoskeleton

The structure and conformational dynamic changes that occur in cytoskeletal proteins within living cells and evidence for their participation in computational processing are described. The role of cellular automata, in which lattice subunits with discrete states interact only with nearest neighbors, in molecular computing is discussed. Simple rules governing subunit neighbor interactions can lead to complex behaviour capable of computation. It is shown that cellular automata may be implemented in the conformational relationships among neighboring protein subunits of cytoskeletal polymers including microtubules, and microtubule conformational automata networks may signal, adapt, recognize, and subserve neural-level learning     

Scanning tunnelling engineering

The great potential for building molecular scale machines and other structures was first noted by Richard Feynman (1960). He also proposed the development of tools to construct nanoscale mechanisms and devices. The range of technology that he proposed is now called nanotechnology, a term coined by Taniguchi (1974). Emergence of STM and related technology should greatly facilitate the development of nanotechnology in the decades to come. Franks' (1987b) review of nanotechnology notes the tremendous potential of STM-derived tools for what he terms ‘scanning tunneling engineering’. However, STM technology can also augment the ‘bottom up’ approaches to nanotechnology, exemplified for example by Forrest Carter's (1979, 1980, 1982, 1983) proposals for building molecular electronic devices (nanocomputers) using synthetic ‘modular chemistry’ and related techniques of supramolecular chemistry (Kuhn & Mobius, 1971; Kuhn, 1983; Lehn, 1980, 1988). A multi-tip STM system integrated with an optical microscope was proposed in 1986 as a ‘nanotechnology workstation’ suitable for scanning tunnelling engineering (Schneiker & Hameroff, 1988). In this paper, we describe an overview of scanning tunnelling engineering, present concepts for nanosensors and nanoswitches, and discuss design considerations for dual tip STM. Finally, we repeat an announcement of a series of ‘Feynman’ prizes for miniature STM.     

The feasibility of coherent energy transfer in microtubules

It was once purported that biological systems were far too ‘warm and wet’ to support quantum phenomena mainly owing to thermal effects disrupting quantum coherence. However, recent experimental results and theoretical analyses have shown that thermal energy may assist, rather than disrupt, quantum coherent transport, especially in the ‘dry’ hydrophobic interiors of biomolecules. Specifically, evidence has been accumulating for the necessary involvement of quantum coherent energy transfer between uniquely arranged chromophores in light harvesting photosynthetic complexes. The ‘tubulin’ subunit proteins, which comprise microtubules, also possess a distinct architecture of chromophores, namely aromatic amino acids, including tryptophan. The geometry and dipolar properties of these aromatics are similar to those found in photosynthetic units indicating that tubulin may support coherent energy transfer. Tubulin aggregated into microtubule geometric lattices may support such energy transfer, which could be important for biological signalling and communication essential to living processes. Here, we perform a computational investigation of energy transfer between chromophoric amino acids in tubulin via dipole excitations coupled to the surrounding thermal environment. We present the spatial structure and energetic properties of the tryptophan residues in the microtubule constituent protein tubulin. Plausibility arguments for the conditions favouring a quantum mechanism of signal propagation along a microtubule are provided. Overall, we find that coherent energy transfer in tubulin and microtubules is biologically feasible.     

Imaging Fullerene C60 with Atomic Resolution Using a Scanning Tunnelling Microscope

C₆₀ was purified and imaged utilizing scanning tunnelling microscopy (STM) in a constant current mode. By fixing the Fullerenes on the substrate (“frozen state” - no movement or rotation), direct imaging of C₆₀ with atomic resolution was possible, showing one pentagon and one hexagon carbon ring of C₆₀.     

用全面集成方法保证企业安全

Random Walk in Network病毒攻击自1987年前后出现以来,迅速地变本加厉。据估计,目前正在流行的病毒有10万种,另外每月还产生200种新病毒,因此在对付病毒上不能有丝毫懈怠。CA的调研表明,3年前每1500封电子邮件中仅有1封带有被病毒感染的附件。而现在,每15封邮件中就有1封多的邮件附件被感染。这与ICSA实验室第七届计算机病毒流行程度调查年会上宣布的结果是一致的。ICSA实验室发现,目前有83%的病毒是通过电子邮件传播的。损失也很惊人:ILOVEYOU”病毒带来90亿美元损失、“Sircam”10亿、“CodeRed”20亿。病毒、蠕虫和恶意代码的…     

Eyelid imbrication. An unrecognized cause of chronic ocular irritation

BACKGROUND: Eighteen patients with chronic ocular irritation were examined over a 3-year period. All patients demonstrated papillary conjunctivitis and, occasionally, tarsal ulcers. Six also had floppy eyelid syndrome. Underlying every patient's symptoms was the overriding or imbrication of a lax upper eyelid on an often equally lax lower eyelid, allowing lower eyelid lashes to chronically rub the upper eyelid tarsal conjunctiva. METHODS: Chronic ocular irritation in five patients was managed with ocular lubricants. Two of these patients had floppy eyelid syndrome and required nightime shielding for nocturnal eyelid eversion. Thirteen patients underwent eyelid surgery to correct the overriding upper eyelid. Surgical procedures included full-thickness upper eyelid wedge resection, lateral canthal tendon plication, and lower eyelid horizontal shortening, using a tarsal strip procedure. RESULTS: Follow-up averaged 2.5 years. Symptomatology was adequately controlled in all patients. In addition to the five patients who received medical treatment for their symptoms, two with complicated ocular problems required continued ocular lubrication after surgery. Seven patients were successfully treated with eyelid shortening procedures and lateral canthal tendon plication. The remaining six patients underwent a variety of additional eyelid surgeries. All patients undergoing surgery had complete resolution of eyelid imbrication. CONCLUSIONS: Eyelid imbrication is a previously unrecognized cause of chronic ocular irritation. In this condition, eyelid laxity causes the upper eyelid to override the lower eyelid, allowing the lower eyelid to chronically rub and chafe the upper eyelid tarsal conjunctiva. In some cases, symptoms can be managed medically. More often, surgical intervention is required to correct eyelid laxity and prevent overriding of the upper eyelid.     

STM imaging of molecular collagen and phospholipid membranes

The application of STM to biological materiais has been limited by poor conductivity, sample geometry and stability of biological materials. In this paper we describe an STM study of the monomeric helical forms of collagen, a stable, conductive and widely prevalent structural protein. We have also used STM to image artificial Langmuir DPE (dipalmitoyl phosphatidyl ethanolamine) phospholipid membranes. Both molecular collagen and the phospholipid membranes were dried in air on highly oriented pyrolytic graphite (HOPG). Our STM images of collagen dried on HOPG reveal strands 15Å in diameter with a periodicity of about 30Å which correlates with that known to occur in collagen. Spikes which periodically protrude from strands in our STM images of collagen appear to represent pyrrolidine ring structures in the amino acids proline and hydroxyproline. Thus, we report the first STM imaging of native biomolecules revealing intramolecular details and what appear to be specific amino acids. STM imaging of phospholipid membranes show a lattice pattern with densities spaced ～4–5Å apart. These are thought to represent individual phospholipid molecules in an artificial membrane formed on the HOPG. We believe STM and its related technologies will have great future utility in biomolecular studies.