Uv 2250 uv vis spectrophotometer

The CT-DNA solution was prepared, and its concentration was determined from the UV absorbance at 260 nm using molar extinction coefficient ε₂₆₀ = 6600 M⁻¹ cm⁻¹ following the protocol of Ghosh et al. [12 (link), 13 (link)]. The absorbance at 260 and 280 nm was recorded to determine the purity of DNA solution where the A₂₆₀/A₂₈₀ ratio > 1.85 depicting that the DNA was sufficiently free from protein [14 (link)]. Various concentrations of DNA were used to obtain a varied molar ratio of the DNA-compound adduct. Absorbance values were recorded on a double beam UV-2250 UV—VIS spectrophotometer (Shimadzu, Japan). Absorption titration experiments were conducted by keeping the concentration of calothrixin B or its thia analogues as constant (3× 10⁻⁵ mol L^-1) while varying the CT-DNA concentration from 0 to 1 × 10⁻⁴ mol L^-1. Absorbance values were recorded after each successive addition of DNA solution.

The absorbances of β-CD, CSE, the physical mixture of CSE/β-CD, and the CSE/β-CD inclusion complex were measured on a Shimadzu UV-2250 UV-vis spectrophotometer (Kyoto, Japan) ranging from 200 to 400 nm. All the samples were dissolved in 10 mL of water to obtain four sample solutions with a concentration of 1.00 mg/mL, respectively.

¹H and ¹³C NMR spectra were collected on a 400 MHz NMR spectrometer which operated at 400 MHz for ¹H and 100 MHz for ¹³C (Bruker Company). Mass spectra were recorded on a Microflex MALDI-TOF mass spectrometer (Bruker Daltonics). High-resolution mass spectra were obtained from a triple quadrupole GC/MS (Agilent Technologies). Elemental analysis was obtained from a CHNS/O analyzer (Flash 2000, Thermo Scientific). Absorption spectra were obtained from a UV-2250 UV-Vis Spectrophotometer (SHIMADZU, Japan) and emission spectra were obtained from a Carry Eclipse Fluorescence Spectrophotometer (Agilent Technologies). The absolute fluorescence quantum yields and lifetimes were determined using FLS980 Spectrometer (Edinburgh Instruments). The pH buffers were measured from an Ohaus pH meter. Amounts of Hg(ii) ion in water samples were verified by an inductively coupled plasma-optical emission spectrometer (ICP-OES) (iCAP 6500, Thermo Scientific).