Single-molecule experiment

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A single-molecule experiment investigates the properties of a single individual molecule that can be isolated or distinguished for the purpose of an experiment or analysis. Single-molecule studies may be contrasted with measurements on an ensemble or bulk collection of molecules, where the individual behaviour can not be distinguished, and only average characteristics can be measured. Although most measurement techniques are not sensitive enough to observe single molecules, single-molecule fluorescence has emerged as a useful tool for probing various processes which cannot be fully understood on the bulk level, such as the movement of myosin on actin filaments in muscle tissue or the details of individual local environments in solids. In the gas phase at ultralow pressures, single-molecule experiments have been around for decades, but in the condensed phase only in the last 20 years with the groundbreaking work by W. E. Moerner and Michel Orrit has it seen fruition.

1 History
2 Theory
3 Impact
4 Single-molecule effects
5 Single-molecule techniques
6 External links

[edit] History

Many techniques have the ability to observe one molecule at a time, most notably mass spectrometry, where single ions are detected. Spectroscopically, however, the observation of one molecule require that the molecule be in an isolated environment and that it emit photons upon excitation, which oweing to the technology to detect single photons by use of photomultiplier tubes (PMT) or avalanche photodiodes (APD), enables one to record photon emission events with great sensitivity and time resolution.

[edit] Theory

Single molecule spectroscopy uses the fluorescence of a molecule to record information pertaining to its environment, structure, and position. The technique affords the ability to obtain information otherwise not available due to ensemble averaging of a bulk material.