Excitation–emission matrix spectroscopy was used as a rapid, nondestructive, and sensitive method to provide information about the fluorescing fraction of the NOM. Absorbance spectra of dissolved NOM solutions were measured from 200 to 800 nm on a Varian Cary 300UV spectrophotometer in 1 cm quartz cells. Fluorescence spectra were acquired on a Varian Eclipse spectrofluorometer. Excitation wavelengths were sampled from 240 to 450 nm at 5 nm intervals; emission wavelengths were sampled every 2 nm from 300 to 600 nm. A Milli-Q water blank was subtracted from each absorbance and fluorescence measurement. Milli-Q water had an 18 MΩ resistivity and <5 ppb TOC. Samples were diluted if the absorbance in a 1 cm cell was greater than 0.4 at 240 nm. Corrections for fluorescence were made for lamp excitation intensity and detector emission responses, and afterward, corrections for inner filter effects were applied using standard approaches.48 (link) Finally, the results were calibrated first to the water Raman signal of each instrument and then in quinine sulfate units (QSU). Fluorescence results were processed with an in-house MATLAB script (MathWorks, Natick, MA). Dissolved NOM was quantified by measuring the dissolved organic carbon (DOC) via automated heated-persulfate oxidation following an additional filtration through a 0.45 μm polyvinylidene fluoride filter.
Cary 300 uv spectrophotometer
Manufactured by Agilent Technologies
Sourced in United States
The Cary 300 UV spectrophotometer is a high-performance instrument designed for accurate and precise spectroscopic analysis. It measures the absorption or transmission of light by a sample across a range of ultraviolet and visible wavelengths.
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4 protocols using cary 300 uv spectrophotometer
1
Excitation-Emission Matrix Spectroscopy of NOM
2
RNA Duplex Thermal Stability Analysis
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Tm experiments were performed using a CARY 300 UV Spectrophotometer (Varian Inc., Palo Alto, CA, USA) equipped with a Peltier temperature controller and thermal analysis software. The samples were prepared by mixing ON solutions of RNA sense and antisense strands together to give 1.5 µM final concentration in 1 mL of 10 mM sodium cacodylate buffer, 100 mM NaCl, pH 7 in a 1 cm path length quartz cell. A heating–cooling–heating cycle in the 0–90 °C temperature range with a gradient of 0.5 °C min-1 was applied. Tm values were determined from the maxima of the first derivative plots of absorbance recorded at 260 nm versus temperature. The Tm values from two independent experiments were accurate within ± 0.5 °C.
3
Algal Pigment Extraction and Quantification
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Algal cultures (25 mL) were harvested, under dim green light, 72 h after the beginning of the treatments by gentle filtration on 0.8µm filter membrane (Polytetrafluoroethylene; Xingya Purifying Materials Factory; Shanghai, China), and placed in 2 mL Eppendorf tubes covered with aluminum foil, then rapidly immersed into liquid nitrogen and kept at -80 °C until analysis. Extractions of the pigments were done by adding 2 mL of acetone 90% overnight at -20 °C prior to analysis. Ultrasonic probe was used to break the cells (3 W/cm 2 for 20 s; Sonic dismembrator Model 100, Fisher Scientific). The extracts were centrifuged at 4 °C for 10 min (10000×g) and the supernatant was kept for quantification of chlorophyll (Chl a) and carotenoid (Car).
Using Cary 300 UV spectrophotometer (Varian, USA) each extract was scanned between 400-750nm. Independent triplicates were sampled for each culture. The contents of Chl a and carotenoids were calculated according to Jeffrey and Humphrey (1975) and Seely et al. (1972) respectively.
Using Cary 300 UV spectrophotometer (Varian, USA) each extract was scanned between 400-750nm. Independent triplicates were sampled for each culture. The contents of Chl a and carotenoids were calculated according to Jeffrey and Humphrey (1975) and Seely et al. (1972) respectively.
4
Antioxidant Enzyme Assay in Microalgae
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After pesticide exposure (72h), microalgal cultures (50 mL) were centrifuged at 15000×g for 25 min at 4 °C, and the pellet was kept into a 2 mL microtube covered with aluminum foil. After adding 1 mL extraction buffer, samples were immediately plunged into liquid nitrogen and kept at -80 °C until analysis. For each extracted sample enzyme activities were determined with Cary 300 UV spectrophotometer (Varian, USA). Cells were broken with the help of liquid nitrogen, grinding one time, and were then centrifuged at 15000×g for 25 min at 4 °C prior to analysis. Each sample was divided into three replicates for analyzing the superoxide dismutase (SOD) and catalase (CAT) according to Vitoria et al. (2001) and Rao et al. (1996) respectively.
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