University of Rochester researchers are setting a new standard when it comes to producing ultrafast laser pulses over a broader range of wavelengths than traditional laser sources.

In work published in Physical Review Letters, William Renninger, an assistant professor of optics, along with members of his lab, describe a new device, called the “stretched-pulse soliton Kerr resonator,” that enhances the performance of ultrafast laser pulses. The work has important implications for a range of engineering and biomedical applications, including spectroscopy, frequency synthesis, distance ranging, pulse generation, and others.

The device creates an ultrafast laser pulse—on the order of femtoseconds, or one quadrillionth of a second—that’s freed from the physical limits endemic to sources of laser light—what laser scientists call laser gain—and the limits of the sources’ wavelengths.

CRISPR-guided DNA cytosine and adenine base editors are widely used for many applications^1,2,3,4 but primarily create DNA base transitions (that is, pyrimidine-to-pyrimidine or purine-to-purine). Here we describe the engineering of two base editor architectures that can efficiently induce targeted C-to-G base transversions, with reduced levels of unwanted C-to-W (W = A or T) and indel mutations. One of these C-to-G base editors (CGBE1), consists of an RNA-guided Cas9 nickase, an Escherichia coli –derived uracil DNA N-glycosylase (eUNG) and a rat APOBEC1 cytidine deaminase variant (R33A) previously shown to have reduced off-target RNA and DNA editing activities^5,6. We show that CGBE1 can efficiently induce C-to-G edits, particularly in AT-rich sequence contexts in human cells. We also removed the eUNG domain to yield miniCGBE1, which reduced indel frequencies but only modestly decreased editing efficiency. CGBE1 and miniCGBE1 enable C-to-G edits and will serve as a basis for optimizing C-to-G base editors for research and therapeutic applications.