Development of gene-in-plasmid DNA reference materials certified by single-molecule counting.

The mole, the SI unit for measuring the amount of a substance, was redefined as a fixed number of entities. This definition enables straightforward quantification of substances by counting individual entities. Counting proves particularly effective for quantifying large and discrete biological entities such as DNA, proteins, viruses, and cells, which are challenging to quantify via traditional physical or chemical methods.

Precise RNA Quantification by Counting Individual RNA Molecules Using High-Sensitivity Capillary Flow Cytometry.

Precise determination of ribonucleic acid (RNA) concentration without the need for calibration was pursued by sequence-specific counting of individual RNA molecules. This approach eliminates the reverse transcription (RT) step required for polymerase chain reaction (PCR)-based quantification, which may hamper accurate measurements owing to uncertain yields of RT reactions. Target RNAs were tagged with a number of fluorescent oligonucleotide probes with complementary sequences.

Switched integration amplifier-based photocurrent meter for accurate spectral responsivity measurement of photometers.

This work introduces a switched integration amplifier (SIA)-based photocurrent meter for femtoampere (fA)-level current measurement, which enables us to measure a 10 dynamic range of spectral responsivity of photometers even with a common lamp-based monochromatic light source. We described design considerations and practices about operational amplifiers (op-amps), switches, readout methods, etc., to compose a stable SIA of low offset current in terms of leakage current and gain peaking in detail.

Polarization coupling in a highly birefringent photonic crystal fiber by torsional acoustic wave.

We demonstrate and analyze the acousto-optic coupling between two optical polarization modes of the LP(01) mode propagating in a highly birefringent photonic crystal fiber. The coupling is realized based on wavelength selective acousto-optic coupling by traveling torsional acoustic wave in an all-fiber tunable polarization filter configuration. The dispersion properties of the torsional acoustic wave in the photonic crystal fiber and the influence of axial non-uniformity in the modal birefringence on the filter transmission are discussed in detail.