Signature molecular similarity methods

The basic idea of alignment-free shape matching is that a set of rotation- and translation-free descriptors are calculated for con-formers under consideration, and then some similarity measure is devised to quantify the similarity between two molecular objects. Zauhar s shape signatures (45), Breneman s PEST and PESD methods (54-56), the USR (ultrafast shape recognition) method... 

The first step is similar to the classical sensing method the value of a physical quantity in the sensing medium is measured, for example the output voltage of a chemical sensor. Then the microscopic spontaneous fluctuations of these measurements are strongly amplified (typically 1-100 million times) and the statistical properties of these fluctuations are analyzed. These fluctuations are due to the dynamically changing molecular-level interactions between the odor molecules and the sensing media, thus they contain the chemical signature of the odor. The results are compared with a statistical pattern database to identify the odor. 

---