Molecular probes offer researchers a new tool to gather information about the fundamental actions and reactions that occur in cells and molecules. By using fluorescent probes that are compatible with biological material, researchers can obtain color images of cellular and molecular activity. One form of molecular probe that has generated recent interest is semiconductor nanocrystals. These microscopic particles exhibit unique optical properties that offer major advantages over conventional fluorescent dyes for imaging biological samples.
Nanocrystals that transmit light near the infrared (IR) region of the spectrum are especially useful for biological applications, because near-IR light penetrates deeply into body tissues and produces little of the background "noise" that can obscure a light signal. Unfortunately, some nanocrystals synthesized to emit near-IR light signals are toxic, unstable, and susceptible to light bleaching. By specially coating these light beacons, a group of scientists has found a way to suppress their toxicity, maintain and improve their ability to transmit light, and limit photobleaching. The new coatings make nanocrystals highly efficient at transmitting light in the near-IR region.
Another research group, using molecular beacons, has developed a simple method to measure RNA synthesis in real time. This new approach will aid in the understanding of various mechanisms that control RNA and protein production in cells. Once scaled up to high-throughput formats, the measurement of RNA synthesis will be useful in identifying new drugs that inhibit RNA production by bacteria or viruses. In addition, assays might be developed to identify an infectious agent and then quickly determine which antibiotics might be effective or ineffective against the particular strain that is present.
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