Abstract: Provided are compositions comprising recombinant DNA polymerases that include amino acid substitutions, insertions, deletions, and/or exogenous features that confer modified properties upon the polymerase for enhanced single molecule sequencing. Such properties can include enhanced metal ion coordination, reduced exonuclease activity, reduced reaction rates at one or more steps of the polymerase kinetic cycle, decreased branching fraction, altered cofactor selectivity, increased yield, increased thermostability, increased accuracy, increased speed, increased readlength, and the like. Also provided are nucleic acids which encode the polymerases with the aforementioned phenotypes, as well as methods of using such polymerases to make a DNA or to sequence a DNA template.

Abstract: Compositions, kits, methods and systems for single molecule nucleotide sequencing comprising producing polymerase reactions having monovalent cations that control the median pulse width for incorporated nucleotides are disclosed. The levels of alkali metals such as lithium, sodium, potassium, rubidium, and cesium in the polymerization are used to control pulse width while allowing other sequencing parameters to remain within a desirable range.

Abstract: Methods, Compositions, and Systems are provided for nucleic acid sequencing where the sequential incorporation of nucleotides uses two distinct chemical steps. A plurality of nucleotide analogs, each having a labeled leaving group at its 3? hydroxyl can be sequentially added to a growing strand in the presence of a selective cleaving activity that cleaves the 3? hydroxyl leaving group preferentially after it has been incorporated. The selective cleaving agent can comprise an exonuclease activity, and the exonuclease activity can be a polymerase-associated exonuclease activity. Nucleotide analogs having labels on both a cleavable polyphosphate portion and on a 3? hydroxyl leaving group can provide signals characteristic of nucleotide analog incorporation. Systems having illumination optics, collection optics, and substrates observe signals from the labels as they are being incorporated into a growing nucleic acid strand, allowing for the sequencing of template nucleic acids.

Abstract: Methods, compositions, and systems are provided for characterization of modified nucleic acids. In certain preferred embodiments, single molecule sequencing methods are provided for identification of modified nucleotides within nucleic acid sequences. Modifications detectable by the methods provided herein include chemically modified bases, enzymatically modified bases, abasic sites, non-natural bases, secondary structures, and agents bound to a template nucleic acid.

Abstract: Methods, compositions, and systems are provided for characterization of modified nucleic acids. In certain preferred embodiments, single molecule sequencing methods are provided for identification of modified nucleotides within nucleic acid sequences. Modifications detectable by the methods provided herein include chemically modified bases, enzymatically modified bases, abasic sites, non-natural bases, secondary structures, and agents bound to a template nucleic acid.

Abstract: Provided are methods for enhanced sequencing of nucleic acid templates. Also provided are reaction conditions that increase branching fractions during polymerization reactions. Also provided are compositions comprising modified recombinant polymerases that exhibit branching fractions that are higher than the branching fractions of the polymerases from which they were derived. Provided are compositions comprising modified recombinant polymerases that exhibit delayed translocation relative to the polymerases from which they were derived. Also provided are compositions comprising modified recombinant polymerases that exhibit increased nucleotide or nucleotide analog residence time at an active site of the polymerase. Provided are methods for generating polymerases with the aforementioned phenotypes and methods of using such polymerases to sequence a DNA template or make a DNA.