Lambda phage

Summary

Enterobacteria phage λ (lambda phage, coliphage λ, officially Escherichia virus Lambda) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). It was discovered by Esther Lederberg in 1950. The wild type of this virus has a temperate life cycle that allows it to either reside within the genome of its host through lysogeny or enter into a lytic phase, during which it kills and lyses the cell to produce offspring. Lambda strains, mutated at specific sites, are unable to lysogenize cells; instead, they grow and enter the lytic cycle after superinfecting an already lysogenized cell. The phage particle consists of a head (also known as a capsid), a tail, and tail fibers (see image of virus below). The head contains the phage's double-strand linear DNA genome. During infection, the phage particle recognizes and binds to its host, E. coli, causing DNA in the head of the phage to be ejected through the tail into the cytoplasm of the bacterial

Official source

https://en.wikipedia.org/wiki/Lambda_phage

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Carbon electrodes have recently been introduced as an alternative to metal electrodes and insulator structures for dielectrophoretic applications. Here, an experimental and theoretical study employing an array of 3D carbon electrodes contained in a microfluidic channel for the dielectrophoretic manipulation of DNA is presented. First evidence that carbon-electrode DEP can be used for the manipulation and trapping of biomolecules such as DNA is reported. In particular, the dielectrophoretic response of λ-DNA (48.5 kbp) under various frequencies and flow conditions necessary for retention of λ-DNA are studied. Negative DEP is observed at frequencies above 75 kHz and positive DEP is present in the range below 75 kHz and down to 5 kHz. We further implement a theoretical model to capture the experimental findings in sufficient detail. Our theoretical considerations based on reported scaling laws for linear and supercoiled DNA further suggest that carbon-electrode DEP devices could be employed in future analytical applications such as DNA preconcentration and fractionation.

Wiley-Blackwell2013

The enhancement of DNA fragmentation in a bench top ultrasonic water bath with needle-induced air bubbles: Simulation and experimental investigation

Martinus Gijs, Thomas Lehnert, Yang Liu, Lin Sun

Shearing DNA to a certain size is the first step in many medical and biological applications, especially in next-generation gene sequencing technology. In this article, we introduced a highly efficient ultrasonic DNA fragmentation method enhanced by needle-induced air bubbles, which is easy to operate with high throughput. The principle of the bubble-enhanced sonication system is introduced and verified by flow field and acoustic simulations and experiments. Lambda DNA long chains and mouse genomic DNA short chains are used in the experiments for testing the performance of the bubble-enhanced ultrasonic DNA fragmentation system. Air bubbles are an effective enhancement agent for ultrasonic DNA fragmentation; they can obviously improve the sound pressure level in the whole solution, thus, achieving better absorption of ultrasound energy. Growing bubbles also have a stretched function on DNA molecule chains and form a huge pressure gradient in the solution, which is beneficial to DNA fragmentation. Purified lambda DNA is cut from 48.5 to 2 kbp in 5 min and cut to 300 bp in 30 min. Mouse genomic DNA (asymptotic to 1400 bp) decreases to 400 bp in 5 min and then reduces to 200 bp in 30 min. This bubble-enhanced ultrasonic method enables widespread access to genomic DNA fragmentation in a standard ultrasonic water bath for many virus sequencing demands even without good medical facilities. Published under an exclusive license by AIP Publishing.

AIP Publishing2022

Screening of a Human Antibody Phage Display Library Against a Peptide Antigen Using Stimuli-Responsive Bioconjugates

Dorothée Dumoulin, Caroline Vandevyver

A synthetic antibody phage library, (ETH-2) was screened against the MUC-1 peptide. Two standard methods were used, namely screening on immunotubes coated with the peptide antigen and on streptavidin-coated paramagnetic particles together with a biotinylated MUC-1 peptide. The results were compared with those obtained using a novel approach based on a stimuli-responsive bioconjugate of avidin and poly-(N-isopropylacrylamide), also in combination with the biotinylated peptide. The poly-(N-isopropylacrylamide)-based bioconjugate is soluble below a temperature of 30 degrees C in the aqueous solutions pertinent to this study, but precipitates rapidly once this temperature is surpassed. The process is reversible, and the bioconjugate redissolves once the temperature is lowered again. The stimuli-responsive bioconjugate was used to isolate specific phage from the library in several rounds of panning, consisting of repeated thermoprecipitation/redissolution cycles in a procedure known as "affinity precipitation." As Jar as we know, this is the first time a compound as big as a viral particle has been specifically captured by a stimuli-responsive bioconjugate. Compared to the two other investigated screening techniques, affinity precipitation of the phage led to a greater variety of genetically, different specific phage, while the process was easy to handle and required no dedicated equipment safe for a centrifuge and a thermostated water bath.

2008