Medical Articles

Gene therapy has been considered to be a powerful approach for the prevention and/or treatment of a variety of diseases from genetic disorders, infections, to cancer. The success of gene therapy in the clinic is largely limited currently, mainly due to the lack of safe and efficient delivery vectors. Despite the high transfection efficiency, viral vectors encounter the vital toxicity issues and production problems. Increasing endeavors have been therefore directed towards the development of non-viral systems with the advantages of low immunogenicity and toxicity, ease in manufacturing and mass production, low cost, excellent stability, reduced vector size limitations, high flexibility regarding the size of transgenes to be delivered, and diverse chemical designs for constructing vectors with multiple functions. In this chapter, we summarized most of the synthetic non-viral systems currently employed for gene therapy, including lipid and polymer-based vectors, nanomaterials such as magnetic nanoparticles, quantum dots, gold/silica nanostructures, carbon nanotubes, calcium phosphate nanoparticles, and layered double hydroxides/clays, as well as multifunctional nanosystems among them. Particular attention has been paid on synthetic polymers and the related nanomedicines. Selected clinical trials of gene therapy using non-viral vectors as well as the future development in this rapidly growing field were briefly discussed.

DNA polymerases are highly efficient and accurate macromolecular machines. They are capable of replicating DNA at up to 1,000 nucleotides per second while making less than one error in 100,000 additions. However, DNA is constantly subjected to damage from myriad sources. DNA damage disrupts normal cellular DNA replication by interfering with the accuracy and efficiency of replicative DNA polymerases. Specialized Y family DNA polymerases exist that can copy damaged DNA, although that ability often has a mutagenic cost. Therefore, Y family DNA polymerase activity is highly regulated in the cell. This chapter presents the functions of both replicative and Y family DNA polymerases and the cellular mechanisms of polymerase management. The focus is on systems but also briefly discusses eukaryotic Y family polymerases. We first present DNA replication carried out by prokaryotic DNA polymerase III and describe its subunits and the coordination of leading and lagging strand replication. We then discuss DNA damage and specialized Y family DNA polymerases. Different models for the management of replicative and Y family DNA polymerases are presented. Finally, we briefly compare the eukaryotic systems with their prokaryotic counterparts.

incidence: 4/22, sa. const.: people of Germany, contamination: natural, conc. range: <0.06–0.13 ng/ml, Ø conc.: 0.11 ng/ml, country: Germany

In the last two decades, fundamental and application-driven research on microfluidics and bio-micro-electro-mechanical systems (BioMEMS) has flourished in academia and industries and has begun to make impact on medicine and biosciences. Packaging of these systems is an integral if not critical part of the device/system design and function. Because the applications and the designs of the chips are wide ranging, it is difficult to achieve a universal packaging scheme that meets the requirements of all applications. Instead, research and manufacturing practices of each type of biochip have come up with specialty techniques. This chapter will review these techniques in the specific contexts of the chip applications, as well as materials requirements. In addition, we will highlight common and advanced practices and point out research needs in these areas.

We have analyzed the restriction digest patterns of the mitochondrial DNA from 41 cytoplasmic petite strains of , that have been extensively characterized with respect to genetic markers. Each mitochondrial DNA was digested with seven restriction endonucleases (RI, I, III, HI, I, I, and I) which together make 41 cuts in grande mitochondrial DNA and for which we have derived fragment maps. The petite mitochondrial DNAs were also analyzed with II, III, and I, each of which makes more than 80 cleavages in grande mitochondrial DNA. On the basis of the restriction patterns observed (i.e., only one fragment migrating differently from grande for a single deletion, and more than one for multiple deletions) and by comparing petite and grande mitochondrial DNA restriction maps, the petite clones could be classified into two main groups: (1) petites representing a single deletion of grande mitochondrial DNA and (2) petites containing multiple deletions of the grande mitochondrial DNA resulting in rearranged sequences. Single deletion petites may retain a large portion of the grande mitochondrial genome or may be of low kinetic cimplexity. Many petites which are scored as single continuous deletions by genetic criteria were later demonstrated to be internally deleted by restriction endonuclease analysis. Heterogeneous sequences, manifested by the presence of sub-stoichiometric amounts of some restriction fragments, may accompany the single or multiple deletions. Single deletions with heterogeneous sequences remain useful for mapping if the low concentration sequences represent a subset of the stoichiometric bands. Using a group of petites which retain single continuous regions of the grande mitochondrial DNA, we have physically mapped antibiotic resistance and mit markers to regions of the grande restriction map as follows: C (99.3-1.4 map units)-OXI-1 (2.5-15.7)-OXI-2 (18.5-25)-P (28.1-34.2)-OXI-3 (32.2-61.2)-O (60-62)-COB (64.6-80.8)-O (80.4-85.7)-E (95-98.9).

Nanobiotechnology involves the creation, characterization, and modification of organized nanomaterials to serve as building blocks for constructing nanoscale devices in technology and medicine. Living systems contain a wide variety of nanomachines and highly ordered structures of macromolecules. The novelty and ingenious design of the bacterial virus phi29 DNA packaging motor and its parts inspired the synthesis of this motor and its components as biomimetics. This 30-nm nanomotor uses six copies of an ATP-binding pRNA to gear the motor. The structural versatility of pRNA has been utilized to construct dimers, trimers, hexamers, and patterned superstructures via the interaction of two interlocking loops. The approach, based on bottom-up assembly, has also been applied to nanomachine fabrication, pathogen detection and the delivery of drugs, siRNA, ribozymes, and genes to specific cells and . Another essential component of the motor is the connector, which contains 12 copies of a protein gp10 to form a 3.6-nm central channel as a path for DNA. This article will review current studies of the structure and function of the phi29 DNA packaging motor, as well as the mechanism of motion, the principle of construction, and its potential nanotechnological and medical applications.

One of the recent applications of nanopores is to use them as detectors/analyzers for bio-molecules and nanopore based sequencing has been studied to quickly sequence DNA. In this paper, three categories of forces proposed in the literature to oppose the electrical driving forces in the DNA translocation process are analyzed, (1) the entropic forces of DNA uncoiling/recoiling at the pore entrance/exits, (2) the viscous drag acting on the blob like DNA outside the nanopore, and (3) the viscous drag acting on the linear DNA inside the nanopore. The magnitudes of these forces are calculated based on the parameters used in experiments and it is shown that the first two of the aforementioned categories of forces are usually small compared to the electrical driving force, while the last one is of the same order as the electrical driving force. To evaluate the viscous drag force acting on the linear DNA inside the nanopore, a hydrodynamic model based on the lubrication approximation is used to calculate the flow field and the viscous drag force acting on a DNA immobilized in a nanopore. This model is validated by good agreement with the experimental data for the tethering force used to immobilize a DNA inside the nanopore.

Our results demonstrate that reliable extraction methods for DNA methylation events can be created through corpus annotation and straightforward retraining of a general event extraction system. The introduced resources are freely available for use in research from the GENIA project homepage .

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