ABSTRACT
Methylation of cytosine is a covalent modification of DNA that can be used to silence genes, orchestrating a myriad of biological processes including cancer. We have discovered that a synthetic nanopore in a membrane comparable in thickness to a protein binding site can be used to detect methylation. We observe a voltage threshold for permeation of methylated DNA through a <2 nm diameter pore, which we attribute to the stretching transition; this can differ by >1 V/20 nm depending on the methylation level, but not the DNA sequence.
Subject(s)
DNA Methylation , DNA/chemistry , DNA/metabolism , Membranes, Artificial , Algorithms , Base Sequence , Electrophoresis, Agar Gel , Genes, BRCA1 , Insulin-Like Growth Factor II/genetics , Permeability , Polymerase Chain Reaction , Protein ConformationABSTRACT
We have assembled three-dimensional heterotypic networks of living cells in hydrogel without loss of viability using arrays of time-multiplexed, holographic optical traps. The hierarchical control of the cell positions is achieved with, to our knowledge, unprecedented submicron precision, resulting in arrays with an intercell separation <400 nm. In particular, we have assembled networks of Swiss 3T3 fibroblasts surrounded by a ring of bacteria. We have also demonstrated the ability to manipulate hundreds of Pseudomonas aeruginosa simultaneously into two- and three-dimensional arrays with a time-averaged power <2 mW per trap. This is the first time to our knowledge that living cell arrays of such complexity have been synthesized, and it represents a milestone in synthetic biology and tissue engineering.
