Unidirectional rotation in a mechanically interlocked molecular rotor

Molecular motor proteins are ubiquitous in nature and have inspired attempts to create artificial machines that mimic their ability to produce controlled motion on the molecular level. A recent example of an artificial molecular rotor is a molecule undergoing a unidirectional 120 degrees intramolecular rotation around a single bond; another is a molecule capable of repetitive unimolecular rotation driven by multiple and successive isomerization of its central double bond. Here we show that sequential and unidirectional rotation can also be induced in mechanically interlocked assemblies comprised of one or two small rings moving around one larger ring. The small rings in these [2]- and [3]catenanes move in discrete steps between different binding sites located on the larger ring, with the movement driven by light, heat or chemical stimuli that change the relative affinity of the small rings for the different binding sites. We find that the small ring in the [2]catenane moves with high positional integrity but without control over its direction of motion, while the two rings in the [3]catenane mutually block each other's movement to ensure an overall stimuli-induced unidirectional motion around the larger ring.     

施加岩粉对水稻生态系统植硅体碳的增汇作用(英文)

植硅体态碳(Phyt OC)在植硅体的"保护"作用下,可以长时间地保存在土壤中,是一种长期有效的生物固碳机制.本文通过在盆栽水稻中施加不同水平的岩粉来探讨其对植硅体态碳增汇的影响.通过微波消解法提取植硅体和氢氟酸溶解生物硅测定其植硅体封存的碳含量.结果表明,施加岩粉显著地提高了水稻各器官中植硅体和植硅体态碳含量及其植硅体碳的产生通量.因此,硅营养调控机制(外施硅肥)是一种提高农田生态系统(尤其是稻田)植硅体封存有机碳的潜力、增加土壤中Phyt OC积累速率的有效措施.     

Biochemistry: role of PQQ as a mammalian enzyme cofactor?

The announcement by Kasahara and Kato of a new redox-cofactor vitamin for mammals, pyrroloquinoline quinone (PQQ), was based on their claim that an enzyme, predicted to be involved in mouse lysine metabolism, is a PQQ-dependent dehydrogenase. However, this claim was dependent on a sequence analysis using databases that inappropriately label beta-propeller sequences as PQQ-binding motifs. What the evidence actually suggests is that the enzyme is an interesting novel protein that has a seven-bladed beta-propeller structure, but there is nothing to indicate that it is a PQQ-dependent dehydrogenase.     

Evolution of the 87A and 87C heat-shock loci in Drosophila

Several species related to Drosophila melanogaster have two loci containing sequences which code for the major heat-shock protein of molecular weight 70,000 (hsp70). These sequences are arranged as two pairs of inverted repeats. The structure of the 87C locus in D. melanogaster seems to have arisen through DNA insertion. Hsp70-coding sequences at the two loci are not evolving independently. Gene conversion between hsp70 genes has apparently occurred both within and between loci.     

Reach and grasp by people with tetraplegia using a neurally controlled robotic arm

Paralysis following spinal cord injury, brainstem stroke, amyotrophic lateral sclerosis and other disorders can disconnect the brain from the body, eliminating the ability to perform volitional movements. A neural interface system could restore mobility and independence for people with paralysis by translating neuronal activity directly into control signals for assistive devices. We have previously shown that people with long-standing tetraplegia can use a neural interface system to move and click a computer cursor and to control physical devices. Able-bodied monkeys have used a neural interface system to control a robotic arm, but it is unknown whether people with profound upper extremity paralysis or limb loss could use cortical neuronal ensemble signals to direct useful arm actions. Here we demonstrate the ability of two people with long-standing tetraplegia to use neural interface system-based control of a robotic arm to perform three-dimensional reach and grasp movements. Participants controlled the arm and hand over a broad space without explicit training, using signals decoded from a small, local population of motor cortex (MI) neurons recorded from a 96-channel microelectrode array. One of the study participants, implanted with the sensor 5?years earlier, also used a robotic arm to drink coffee from a bottle. Although robotic reach and grasp actions were not as fast or accurate as those of an able-bodied person, our results demonstrate the feasibility for people with tetraplegia, years after injury to the central nervous system, to recreate useful multidimensional control of complex devices directly from a small sample of neural signals.