Electrophoresis is a method that is extensively used in chemical and biological laboratories. Two-dimensional gel electrophoresis (2DGE) is often exploited for protein analysis. The first dimension is isoelectric focusing (IEF) and the second dimension is polyacrylamide gel electrophoresis (PAGE). The key advantage of 2DGE is its enormous separation resolution. Thousands of protein spots can be detected in a single 2D gel image called 2D map. The major limitations of 2DGE are twofold: (1) reproducibility is poor due to gel warping and diffusion resulting from Joule heating; (2) the processes, which include manual gel polymerization, hours of separation, and staining/destaining, are time-consuming and labor-intensive.

To address the limitations, efforts have been made in applying microfluidics to two-dimensional (2D) electrophoresis. Microfluidics technology has been used to construct miniaturized analytical instruments called "Lab-on-a-chip" devices. The principles of microfabrication and microfluidics, as well as their current and potential applications, have been reviewed recently in Fabrication and Microfluidics.

Common analytical assays, including polymerase chain reaction, protein analysis, DNA separations, and cell manipulations, have been reduced in size and fabricated in a centimeter-scale chip. The size reduction of an analytical instrument has many advantages including high speed of analysis, minimization of required sample and reagents, and ability to operate in a high-throughput format.

from Fan et al (2009) in Biomolecular Separation and Analysis

Bibliography:

1. Lab-on-a-Chip Technology: Fabrication and Microfluidics
2. Lab-on-a-Chip Technology: Biomolecular Separation and Analysis

Labels: electrophoresis, two-dimensional gel electrophoresis

ABC transporters are fascinating molecular machines that use the energy of ATP to catalyze the transport of a tremendous variety of substrates across biological membranes in a vectorial fashion. All ABC transporters analyzed so far are composed of two nucleotide-binding domains (NBD) and two transmembrane domains (TMD) that can be arranged in any possible combination. However, additional transmembrane segments or extended NBDs, raise the possibility that these extensions act as platforms to interact with additional proteins with functional or regulatory consequences.

Recent crystal structures of isolated NBDs in different functional states and the structures of intact ABC transporters have elucidated the three-dimensional architecture, domain-domain interactions and putative signaling pathways in these membrane proteins that guarantee efficient substrate recognition and translocation in an ATP-dependent manner.

from Thorsten Jumpertz, I. Barry Holland and Lutz Schmitt (2009) in ABC Transporters in Microorganisms Edited by Alicia Ponte-Sucre, Caister Academic Press. ISBN: 978-1-904455-49-3

Further reading: ABC Transporters as Targets against Drug Resistance

Labels: molecular machines, nucleotide-binding domains, translocation, two transmembrane domains

The basic tool of most microfabrication technology is photolithography. Initially, most photolithographic processes were conducted in silicon and these well-developed technologies were directly derived from the semiconductor industry. Recently, diverse non-silicon-based LOC fabrication methods have been developed. The biggest change in microfabrication has occurred in the materials used. In silicon technology, the main materials were silicon wafer, glass, photoresistor and metal which are excellent materials for mass production of integrated circuits. However for biomedical applications these materials and the fabrication processes have some limits due to: (1) the biocompatibility is not fully proven, (2) the cost of material is high, and (3) the fabrication process requires complicated facilities.

To address these limits, diverse microtechnologies employing several materials have been developed. As representative non-silicon materials, several polymers, such as poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA), and cyclo-olefin copolymer (COC), have been used to construct a microstructure. In addition, biological material such as proteins, cells, and antigens can be used as micropatterning material to create biologically relevant patterns on the surfaces of substrates and this technology provides new capabilities for cell biology, the production of biosensors, and tissue engineering.

Recently, the assembly of biohybrid materials from engineered tissues and synthetic polymer thin films was done to perform biomimetic tasks (e.g. tissue based robot) by varying tissue architecture, thin-film shape, and the electrical-pacing protocol. In addition, diverse fabrication methods (e.g. softlithography, stereolithography, in situ polymerization, etc.) and devices (e.g. scanning tunneling microscope, deep reactive ion etching, etc.) have been developed for use in microfabrication technology.

Experimental techniques and associated technology in biology laboratories are evolving to handle small quantities of samples more efficiently and Lab-on-a-Chip (LOC) devices are becoming more widespread. It is becoming increasingly important for all biologists to gain a basic understanding of the technology of the microfabrication process.

from Sang-Hoon Lee (2009) in Lab-on-a-Chip Technology: Fabrication and Microfluidics

Bibliography:

1. Lab-on-a-Chip Technology: Fabrication and Microfluidics
2. Lab-on-a-Chip Technology: Biomolecular Separation and Analysis

Labels: in situ polymerization, microfabricationphotolithography, softlithography, stereolithography