Sample Paper on Single Molecule to Multi-molecule Ensemble

Single molecules have abilities to probe molecular structure, its dynamics, and functions which are not hindered by the averaging inherent in ensemble experiments. In the ensemble experiments, molecules are interrogated simultaneously and their properties observed. There are various research projects carried out by ensembles. First is transporting fluid-state DOPC vesicles at significant velocities. Secondly is a mechanism for hear. Thirdly is in transition force of cancer cells. The other research project carried out by ensemble includes kinetics study and cardiac muscle.

A molecular motor is an enzyme. There are three kinds of molecular motors in cells and one rotation motor. The molecular motors are kinesin, myosin, and dyneism.There are cytoskeleton cells in the molecular motors namely: Actin filament in myosin and microtubules in kinesis and dyneism.Myosins have a wide variety of functions including muscle contraction, vesicle transportation, and cytokinesis and maintaining morphology of organs among others. The body of humans has 39 kinds of myosins in 12 classes. There is structure difference in these myosins.The difference is either processive or nonprocesssive myosin. Myosin Va and myosin Vb are processive while myosin Vc is non-processive.This difference can be demonstrated by a cargo motor. The cargo motor can move a cargo with an acting filament for several microns without dissociating. If myosin V had kinetics like that of myosin II, then a large number of molecules would be needed on the surface. On the other hand, if myosin V worked cooperatively, then single molecules could move the cargo.

Myosin Va and Vb structure and functions can also by use of a fluorescent microscopy. The emission of light through the process of fluorescence is almost a simultaneous process of absorption of the excitation of light and emission of light from the short delay of photon absorption and emission. Fluorescence microscopy uses fluorescence to highlight structures of a living specimen. The structure of myosin Va  is observed using this microscopy. The total reflection fluorescence (TIRF) microscopy is Ez=Eoexp(-z/dz)  with a deep penetration depth of evanescent wave The advantage of TIRF is that it has a wide field of fluorescence.Griscelli’s disease can also be observed using this special kind of light. The “Dilute” mouse is a good model for observation the disease.Griscelli disease is an autosomal disorder characterized by pigmentary dilution, cellular immunodeficiency, and activation of uncontrollable lymphocyte and macrophage. In a dilute-lethal mouse, this disorder emanates as the dilute locus encodes myosin Va.The unconventional myosin encoding genes are characteristics of  Griscelli disease.

Myosin Va is known to move processively along an actin filament. It has two heads, each consisting of a motor domain and an expanded neck domain. Measuring the single mechanical properties, the neck is said to be too short to allow the two heads to span with the actin filament, and the motor domain functions in operating the myosin.

Myosin Vc is expressed in the acinar cells of the pancreas.Lacriminal gland acinar cells are mainly used in regulating secretion of properties. Myosin Vc is revealed to be associated with secretary vesicles. Myosin Vc is also detected to be in association with actin-coated fusion intermediaries. The epithelial cells in acinar cells are very thick and connected to each other.

Xuequn Chen, an assistant professor in Physiology in the school of medicine is one of the researchers of this project.His opinion about myosin Vc is that it takes a low duty ratio. Also, his findings state that multiple Vc molecules may change to a high duty ratio and work together because myosin Vc binds on a large cargo with flat diameter than a small size cargo.