Protein and mRNA copy numbers vary from cell to cell in isogenic bacterial populations. However, these molecules often exist in low copy numbers, and are difficult to detect in single cells. Here we carried out quantitative system-wide analyses of protein and mRNA expression in individual cells with single-molecule sensitivity using a newly constructed yellow fluorescent protein fusion library for Escherichia coli. We found that almost all protein number distributions can be described by the gamma distribution with two fitting parameters which, at low expression levels, have clear physical interpretations as the transcription rate and protein burst size. At high expression levels, the distributions are dominated by extrinsic noise. Strikingly, we found that a single cell's protein and mRNA copy numbers for any given gene are uncorrelated.Gene expression is often stochastic because gene regulation takes place at a single DNA locus within a cell. Such stochasticity is manifested in fluctuations of mRNA and protein copy numbers within a cell lineage over time, and in variations of mRNA and protein copy numbers among a population of genetically identical cells at a particular time (1,2,3,4). Because both manifestations of stochasticity are connected, measurement of the latter allows the deduction of the gene expression dynamics in a cell (5). We aim to characterize such mRNA and protein distributions in single bacteria cells at a system-wide level.While single cell mRNA profiling has been carried out with cDNA microarray (6) and mRNA-seq (7), these studies did not have single molecule sensitivity and are not suitable for bacteria, which express mRNA at low copy numbers (8). A fluorescent protein reporter library of Saccharomyces cerevisiae (9) has proven to be extremely useful in protein profiling (10,11). However, the lack of sensitivity in existing flow cytometry or fluorescence microscopy techniques prevented the quantification of one third of the labeled proteins because of their low copy numbers. In recent years, single-molecule fluorescence ** Publisher's Disclaimer: This manuscript has been accepted for publication in Science. This version has not undergone final editing. Please refer to the complete version of record at http://www.sciencemag.org/. The manuscript may not be reproduced or used in any manner that does not fall within the fair use provisions of the Copyright Act without the prior, written permission of AAAS." † To whom correspondence should be addressed. xie@chemistry.harvard.edu. * These authors contributed equally to this work. NIH Public Access Author ManuscriptScience. Author manuscript; available in PMC 2010 August 17. Single-molecule imaging of a YFP reporter libraryWe created a chromosomal YFP fusion library (Fig. 1A), in which each strain has a particular gene tagged with the YFP coding sequence. YFP can be detected with single molecule sensitivity in live bacterial cells (8,18). We converted the C-terminus tags of an existing chromosomally affinity-tagged E. coli library (19,20...

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Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

The authors demonstrated that N , NЈ-ditridecyl-3,4,9,10-perylenetetracarboxylic diimide ͑PTCDI-C13͒ thin-film transistors ͑TFTs͒ exhibited high field-effect electron mobility of 2.1 cm 2 / V s by just annealing at an adequate temperature ͑140°C͒ after the TFT fabrications. While PTCDI-C13 formed c-axis oriented thin films, the thermal treatments improved crystallinity of the thin films as revealed by x-ray diffraction. The thermal treatment also affected thin-film morphologies; the morphologies changed from oval ball-like grains to flat and large tilelike grains, which had molecular height steps and whose size reached several micrometers.

We have determined crystallographic structures of four thiophene/phenylene co-oligomers with different molecular shapes. The compounds consist of the molecules straight, bent, or zigzag. All the crystals are monoclinic with space group either P21/c or P21/n, Z = 4, and the unique axis of b. The crystals are characterized by the presence of the molecular layered structure in which the molecules form the well-known herringbone structure laterally spreading along the ab-plane. We investigate the molecular disposition in the crystals and present its peculiarity in relation to those comprising nonstraight molecules (e.g., bent or zigzag). The specific effects upon optical characteristics produced by this peculiarity are mentioned.