Single molecule enzymology

酶是允许细胞在生理条件下以适当的速度发生反应的分子。细胞的健康完全取决于这些反应。然而，由于细胞的需求随着条件的不同而变化，因此维持细胞的许多反应的速率也必须改变。由于是酶控制了这些速率，因此细胞必须能够调节这些酶，以确保细胞的所有要求都得到适当的满足。 由于分子如此之小，化学研究通常涉及对大量看似相同的分子进行测量。所有获得的数据都反映了被测量特性的平均值。如果单个分子之间存在差异，则由于非常大的平均尺度，它们不会被检测到。 在过去的几年里，科学家们已经开发出了测量包括酶在内的单个分子特征的方法。对于酶，有一个有趣的发现：给定酶的单个分子不具有相同的性质。这意味着，为了调节其化学成分，细胞必须改变酶群体的特征分布。实现这一目标的手段尚不清楚。 在我的研究中，我们使用酶β-半乳糖苷酶作为模型来研究酶微观异质性背后的结构差异，以及细胞如何改变单个酶分子群体的性质分布以调节其化学。这是通过使用单酶分子测量来完成的。测量了特定处理对酶种群的复合单个分子的分布特性的影响。这样做是为了洞察单个分子之间的结构差异，并确定细胞如何改变属性的分布，以实现总体群体特征的期望变化。这将增加我们对细胞化学是如何控制的，以及这与健康和疾病状态的关系的总体理解。

Enzymes are molecules that allow reactions to occur at the appropriate rate in a cell under physiological conditions. The health of a cell is totally dependent upon such reactions. However, since the requirements of a cell change with differing conditions, so must the rates of many of the reactions sustaining the cell. Since it is enzymes that control these rates, it is essential for a cell to be able to regulate these enzymes to ensure that all of a cell's requirements are being properly met. Since molecules are so small, chemical studies have classically involved measurements made on a very large number of seemingly identical molecules. All the data obtained reflects average values for the characteristics being measured. If differences between individual molecules existed, they would not be detected due to the very large scale averaging. Over the past years, scientists have developed methods to measure the characteristics of individual molecules, including enzymes. With enzymes an interesting finding was made: Individual molecules of a given enzyme do not have identical properties. This means that in order to regulate its chemistry, a cell must alter the distribution of characteristics of an enzyme population. The means by which this is achieved is not understood. In my research we use the enzyme beta-galactosidase as a model to study the structural differences which underlie enzyme microheterogeneity and how a cell can alter the distribution of properties of a population of individual enzyme molecules in order to regulate its chemistry. This is done with the use of single enzyme molecule measurements. The effect of a given treatment on the distribution properties of the composite individual molecules of an enzyme population is measured. This is performed to provide insight into the structural differences between the individual molecules and to determine how the cell can alter the distribution of properties to effect a desired change in the overall population characteristics. This will increase our overall understanding of how cell chemistry is controlled and how this relates to the states of both health and disease.