Zero-mode waveguides provide a powerful technology for studying single-molecule real-time dynamics of biological systems at physiological ligand concentrations. We customized a commercial zero-mode waveguide-based DNA sequencer for use as a versatile instrument for single-molecule fluorescence detection and showed that the system provides long fluorophore lifetimes with good signal to noise and low spectral cross-talk. We then used a ribosomal translation assay to show real-time fluidic delivery during data acquisition, showing it is possible to follow the conformation and composition of thousands of single biomolecules simultaneously through four spectral channels. This instrument allows high-throughput multiplexed dynamics of single-molecule biological processes over long timescales. The instrumentation presented here has broad applications to single-molecule studies of biological systems and is easily accessible to the biophysical community.D etermining the molecular details of the time evolution of complex multicomponent biological systems requires analysis at the single-molecule level because of their stochastic and heterogeneous nature. Ideally, such experiments would track simultaneously the composition of a biological system (bound ligands, factors, and cofactors) and the conformation of the individual molecules in real time. Single-molecule fluorescence methods, such as total internal reflection fluorescence (TIRF) microscopy, allow the observations of the compositional dynamics (through arrival of fluorescently labeled ligands, factors, or cofactors) and conformational dynamics (through FRET) of single-molecular species. However, these traditional singlemolecule methods are hindered by limitations in maximal fluorescent component concentrations (up to 50 nM) (1), limited simultaneous detection (two to three colors) (2-6), and low throughput (a few hundred molecules at most per experiment) (7). As such, the full potential of single-molecule fluorescence to investigate a range of biological problems under physiologically relevant conditions has not yet been harnessed.Zero-mode waveguides (ZMWs) are small metallic apertures patterned on glass substrates that overcome the concentration restrictions by optically limiting background excitation (8). Each ZMW consists of an ∼150-nm-diameter metallic aperture that restricts the excitation light to a zeptoliter volume, making possible experiments with near-physiological concentrations (up to 20 μM) of fluorescently labeled ligands (1). Previous advances in nanofabrication (9), surface chemistry (10), and detection instrumentation (11) have led to ZMW-based instrumentation capable of the direct observation of DNA polymerization (12), reverse transcription (13), processive myosin motion (14), and translation by the ribosome (15, 16) with multicolor single-molecule detection. However, this sophisticated technology has not been broadly available to the scientific community. Despite multiple efforts to develop ZMW instrumentation, the combined difficulties in fabrica...

No abstract

No abstract

A target group of 17 hospitalized male schizophrenics was compared with male student groups of 9 schizotypic, 13 other Minnesota Multiphasic Personality Inventory (MMP1) elevation controls, and 14 normal subjects on a replication of the Rodnick and Shakow (1940) reaction time (RT) procedure. Student groups were classified by MMPI criteria and also evaluated for schizotypic socialization deficits on the Lanyon Social Competence Scale (Lanyon, 1967). The results showed that both schizophrenic patients and schizotypic normals displayed earlier RT crossover than did the control student groups, whereas only the hospitalized schizophrenic group showed significantly longer mean RTs. Schizotypic normals also differed significantly from the other student groups on a newly developed individual crossover measure and on the Lanyon Scale. These findings support some earlier studies indicating that crossover may be a useful at-risk marker of schizophrenia and that the overall mean RT latency score obtained on the same task may function as a symptom-severity variable of generalized attention deficit.Perhaps the most stable experimental finding in the extensive research on the psychopathology of schizophrenia has been the consistent demonstration of deficits in attention on the simple reaction time (RT) task as a function of temporal preparatory interval (PI;Neuchterlein, 1977). The initial study by Huston, Shakow, and Riggs (1937) demonstrated greater RT slowing, more intrasubject variability, and earlier crossover in schizophrenic patients. This crossover effect referred to the inability of schizophrenic patients to benefit from the regularity of temporal presentations compared with irregular Pis when the PI duration exceeded 2 to 3 s. Rodnick and Shakow (1940) showed that normal subjects also displayed crossover when the Pis were extended to 25 s, and they developed a set index to maximize schizophrenic deficits. This RT procedure has been used by a number of investigators to study attentional deficits in groups at risk for schizophrenia (Asarnow, Steffy, MacCrimmon, &

Our study examined the relationship between the Minnesota Multiphasic Personality Inventory (MMPI) and the Scale for the Assessment of Positive Symptoms (SAPS; Andreason, 1984) and the Scale for the Assessment of Negative Symptoms (SANS; Andreason, 1983) in patients who met the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) diagnostic criteria for schizophrenia (n = 125). A significant correlation was found between the SAPS Delusions scale and Scale 6 (Paranoia), the SAPS Positive Thought Disorder Scale and Scale F (Infrequency), and the SAPS Positive Thought Disorder and Scale 9 (Hypomania). Additional analysis also shows, however, that severity of symptoms was the best predictor of MMPI scores. Consistent with previous studies, the MMPI appears useful for screening but not for the detailed evaluation of symptomatology of schizophrenic patients.