Cell Cycle Checkpoint Control Protocols
Download Cell Cycle Checkpoint Control Protocols PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Cell Cycle Checkpoint Control Protocols book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages.
Cell Cycle Checkpoint Control Protocols
Author: Howard B. Lieberman
language: en
Publisher: Springer Science & Business Media
Release Date: 2008-02-02
The field of cell cycle regulation is based on the observation that the life cycle of a cell progresses through several distinct phases, G1, M, S, and G2, occurring in a well-defined temporal order. Details of the mechanisms involved are rapidly emerging and appear extraordinarily complex. Furthermore, not only is the order of the phases important, but in normal eukaryotic cells one phase will not begin unless the prior phase is completed successfully. Che- point control mechanisms are essentially surveillance systems that monitor the events in each phase, and assure that the cell does not progress prematurely to the next phase. If conditions are such that the cell is not ready to progress—for example, because of incomplete DNA replication in S or DNA damage that may interfere with chromosome segregation in M—a transient delay in cell cycle progression will occur. Once the inducing event is properly handled— for example, DNA replication is no longer blocked or damaged DNA is repaired—cell cycle progression continues. Checkpoint controls have recently been the focus of intense study by investigators interested in mechanisms that regulate the cell cycle. Furthermore, the relationship between checkpoint c- trol and carcinogenesis has additionally enhanced interest in these cell cycle regulatory pathways. It is clear that cancer cells often lack these checkpoints and exhibit genomic instability as a result. Moreover, several tumor suppressor genes participate in checkpoint control, and alterations in these genes are as- ciated with genomic instability as well as the development of cancer.
Directed Enzyme Evolution
Author: Frances H. Arnold
language: en
Publisher: Springer Science & Business Media
Release Date: 2008-02-02
Directed evolution comprises two distinct steps that are typically applied in an iterative fashion: (1) generating molecular diversity and (2) finding among the ensemble of mutant sequences those proteins that perform the desired fu- tion according to the specified criteria. In many ways, the second step is the most challenging. No matter how cleverly designed or diverse the starting library, without an effective screening strategy the ability to isolate useful clones is severely diminished. The best screens are (1) high throughput, to increase the likelihood that useful clones will be found; (2) sufficiently sen- tive (i. e. , good signal to noise) to allow the isolation of lower activity clones early in evolution; (3) sufficiently reproducible to allow one to find small improvements; (4) robust, which means that the signal afforded by active clones is not dependent on difficult-to-control environmental variables; and, most importantly, (5) sensitive to the desired function. Regarding this last point, almost anyone who has attempted a directed evolution experiment has learned firsthand the truth of the dictum “you get what you screen for. ” The protocols in Directed Enzyme Evolution describe a series of detailed p- cedures of proven utility for directed evolution purposes. The volume begins with several selection strategies for enzyme evolution and continues with assay methods that can be used to screen enzyme libraries. Genetic selections offer the advantage that functional proteins can be isolated from very large libraries s- ply by growing a population of cells under selective conditions.
Atomic Force Microscopy
Author: Pier Carlo Braga
language: en
Publisher: Springer Science & Business Media
Release Date: 2008-02-02
The natural, biological, medical, and related sciences would not be what they are today without the microscope. After the introduction of the optical microscope, a second breakthrough in morphostructural surface analysis occurred in the 1940s with the development of the scanning electron microscope (SEM), which, instead of light (i. e. , photons) and glass lenses, uses electrons and electromagnetic lenses (magnetic coils). Optical and scanning (or transmission) electron microscopes are called “far-field microscopes” because of the long distance between the sample and the point at which the image is obtained in comparison with the wavelengths of the photons or electrons involved. In this case, the image is a diffraction pattern and its resolution is wavelength limited. In 1986, a completely new type of microscopy was proposed, which, without the use of lenses, photons, or electrons, directly explores the sample surface by means of mechanical scanning, thus opening up unexpected possibilities for the morphostructural and mechanical analysis of biological specimens. These new scanning probe microscopes are based on the concept of near-field microscopy, which overcomes the problem of the limited diffraction-related resolution inherent in conventional microscopes. Located in the immediate vicinity of the sample itself (usually within a few nanometers), the probe records the intensity, rather than the interference signal, thus significantly improving resolution. Since the most we- known microscopes of this type operate using atomic forces, they are frequently referred to as atomic force microscopes (AFMs).