1800 spectrophotometer

To determine the concentration of ferrous ions in the solution, a colorimetric method was used. The method relies on the specific reaction of ferrous ions with colorless o-phenanthroline, resulting in an orange-red chelate complex. The reaction was performed in an acetate buffer, stabilizing the formed complex (pH in the range of 2–9). A standard curve was prepared based on the analysis of the minimal salt medium samples containing a known concentration of Fe²⁺ ions. The detection range of this colorimetric method for cations is in the range of 0.001–0.1 mg/dm³, therefore the samples were appropriately diluted before measurements. The absorbance was measured at a wavelength of 510 nm using a Shimadzu 1800 Spectrophotometer (Shimadzu Corporation, Osaka, Japan).

1-(5-Chloro-2-methyl-3-thienyl)-2-(5-formyl-2-methyl-3-thienyl)cyclopentene was prepared and purified according to literature procedures.^{33 (link)} All other reagents were of analytical purity and used without further treatment. Thin-layer chromatography (TLC) analyses were performed on silica-gel plates, and flash chromatography was conducted by using silica-gel column packages purchased from Qing-dao Haiyang Chemical Company, China.
¹H NMR and ¹³C NMR spectra in CDCl₃ were recorded on Brucker AM-400 spectrometers with tetramethylsilane (TMS) as the internal standard. High-resolution mass spectrometry (HR-MS) were measured by Matrix Assisted Laser Desorption Ionization-Time of Flight/Time of Flight Mass Spectrometer (5800). The melting point was measured by micro-melting point instrument SGWX-4. UV-vis absorption spectra were recorded on a Shimadzu 1800 spectrophotometer, while the fluorescent emission spectra were taken with a Shimadzu RF-5301 PC; both spectrophotometers were standardized.

5-Nitroindole, potassium carbonate, bis(p-fluorophenyl) sulfone, SnCl₂·2H₂O, and acetylchloride were purchased from Energy Chemical and used as received without further purification. ¹H NMR and ¹³C NMR spectra were measured on a Bruker 400 L spectrometer in C₂D₆O₆ at room temperature. High-resolution mass spectrometry data were measured by Matrix Assisted Laser Desorption Ionization-Time of Flight/Time of Flight Mass Spectrometer (5800). Elementary analysis was performed on a Thermo Finnigan Flash EA1112. The high-performance liquid chromatography analysis was performed on an Agilent 1260 HPLC system. The mobile phase consisted of methanol and acetonitrile with the flow rate of 1 mL/min. The absorption wavelength used was set at 330 nm. Hundred percent acetonitrile was used as the running buffer.The UV–Vis absorption spectra were recorded on a Shimadzu 1800 spectrophotometer. The emission spectra, time-resolved emission spectra, and transient PL decay characteristics of the samples were recorded on QM40 (PTI, Horiba Scentific). Temperature was controlled by a cryostat (Advanced Research System Inc.). A nitrogen laser (PTI) with an excitation wavelength of 370 nm was used as the excitation source. The fluorescence quantum yields of solution were measured on QM40 with an integrating sphere (φ 150 mm).

UV absorbance of different samples were recorded with a Shimadzu 1800 spectrophotometer (Shimadzu, Tokyo, Japan) equipped with a temperature controller. Melting curves of DNA structures were obtained by measuring the UV absorbance at 260 or 295 nm in buffer pH 7.0 [100 mM NaCl or 100 mM KCl, and 0.5 mM EDTA] in the presence or absence of QW10 peptide at DNA : peptide ratio (1 : 0), (1 : 1), (1 : 2), (1 : 5), and (1 : 10). The T_m values for 4 μM DNA structures were obtained from the UV melting curves as described previously.^{19 (link)} The heating rates were 0.5 °C min⁻¹. The thermodynamic parameters were evaluated from the fit of the melting curves to a theoretical equation for an intramolecular association as described previously.^{19,20 (link)} Before measurement, the samples were heated to 95 °C in water bath and slowly cooled till water attains room temperature and incubated at 4 °C overnight to avoid any non-equilibrium structures. Experiment has been repeated in triplicates to reproduce the data.

PAGE purified grade DNA oligonucleotide and HPLC purified peptide [QQWQQQQWQQ] was purchased from Helix Biosciences. The concentration of the peptide was determined by measuring the absorbance of Trp at the C-terminal at 280 nm at 25 °C. Single-strand concentrations of DNA oligonucleotides were determined by measuring the absorbance at 260 nm at a high temperature using a Shimadzu 1800 Spectrophotometer (Shimadzu, Tokyo, Japan) connected to a thermoprogrammer. Single-strand extinction coefficients were calculated from mononucleotide and dinucleotide data using the nearest-neighbour approximation.^{26,27 (link)}