Flow injection analysis using continuous channel electrophoresis.

Continuous zone electrophoretic separations in narrow channels coupled to small-bore capillaries have been demonstrated and characterized previously. Presented here is the use of this new technique to monitor dynamic chemical changes occurring in a flow injection analysis system. The fundamental aspects of the data that this type of separation generates are discussed in a comparison of static and dynamic analyses. An analysis of a dynamic separation is also provided to thoroughly outline the steps necessary to deconvolute the data. Three types of dynamic analyses, which simulate realistic analytical situations, are then examined in detail. The first of these involves the addition of a mixture of four dansylated amino acids to the flow injection system to provide several different sample duration periods. The second is the staggered addition of short-duration plugs of analyte to the system. The third is the continuous addition of one analyte at different concentrations. Quantitative information generated by these experiments includes the simultaneous determination of the time of analyte contact and its duration of contact with the sampling capillary, identification of analytes based on electrophoretic mobilities, and concentration changes with time. For the addition of a 1.52 mM solution of N epsilon-dansyl-L-lysine, the sample duration and time of analyte contact with the capillary was determined with an error of < 4%. Concentration changes in the FIA system of dansyl-L-arginine over the range of 0.38-3.04 mM are also demonstrated with transitional edges on the time scale of 3-4 s. Qualitatively, the appearance of analyte bands can reveal impurities and fronting or tailing effects as seen in conventional capillary electrophoretic separations. The results demonstrate the ability of the technique to successfully probe dynamic environments.

Observation and quantitation of exocytosis from the cell body of a fully developed neuron in Planorbis corneus.

We have discovered a neuronal system that releases neurotransmitter via exocytosis from the cell body. In the large dopamine cell of the pond snail Planorbis corneus, depolarization induces rhythmic release of dopamine from the cell body. When a stimulant is applied extracellularly or intracellularly in situ to the cell body, transient dopamine concentration packets that appear in a bursting pattern are observed. Dopamine release is calcium dependent and release is on the time scale expected for exocytosis (2 to 4 msec rise times). Quantitation of individual events reveals an average of 818,000 molecules per exocytotic event. As many as 89,000 individual exocytotic events have been observed following a single stimulation of one cell. Neurotransmitter exocytosis from the neuronal cell body appears to represent an alternative form of neurocommunication to synaptic transmission.