Background: Cancer epidemiology articles often point out that cancer rates tend to be higher among males than females yet rarely is this theme the subject of investigation. Methods: We used the Surveillance, Epidemiology and End Results program data to compute age-adjusted (2000 U.S. standard population) sex-specific incidence rates and male-to-female incidence rate ratios (IRR) for specific cancer sites and histologies for the period 1975 to 2004. Results: The 10 cancers with the largest male-to-female IRR were Kaposi sarcoma (28.73), lip (7.16), larynx (5.17), mesothelioma (4.88), hypopharynx (4.13), urinary bladder (3.92), esophagus (3.49), tonsil (3.07), oropharynx (3.06), and other urinary organs (2.92). Only 5 cancers had a higher incidence in females compared with males: breast (0.01), peritoneum, omentum, and mesentery (0.18), thyroid (0.39), gall-
Semiconductor quantum dots (QDs) have proven to be superior probes for single molecule imaging compared to organic or genetically encoded fluorophores, but they are limited by difficulties in protein targeting, their larger size and on-off blinking. Here, we report compact aqueous CdSe/CdS QDs with significantly improved bioconjugation efficiency and superior single-molecule optical properties. We have synthesized covalent protein labeling ligands (i.e., SNAP tags) that are optimized for nanoparticle use, and QDs functionalized with these ligands label SNAP-tagged proteins ~10-fold more efficiently than existing SNAP ligands. Single-molecule analysis of these QDs shows 99% of time spent in the fluorescent on state, ~4-fold higher quantum efficiency than standard CdSe/ZnS QDs, and 350 million photons detected before photobleaching. Bright signals of these QDs enable us to track the stepping movement of a kinesin motor in vitro and the improved labeling efficiency enables tracking of single kinesins in live cells.
Molecular motors move processively along cytoskeletal filaments through stepping of their catalytic head domains. Observation of the stepping movement of the heads reveals the mechanism of motor processivity and how they coordinate the cycles of the catalytic heads during processive motility. This chapter will discuss recent developments in simultaneous observation of the stepping motions of the two heads using multicolor single particle tracking microscopy.
MspA's narrow constriction, we observe currents unique to the bases within the constriction. We find that both, thermal fluctuations and the geometry of MspA, ensure that these currents are governed by~4 sequential nucleotides. Furthermore, we find that Angstrom-level changes in the position of the DNA within the constriction considerably influence these currents. By varying the voltage we can stretch the DNA and thereby adjust the average position of the DNA within the pore. Our findings improve nanopore sequencing and highlight the power of nanopore technology to probe Angstrom-level distance scales.
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