Fluorescent properties of low-molecular-weight fractions from chernozem humic acids |
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| Authors: | O A Trubetskoi D V Demin O E Trubetskaya |
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| Institution: | 1. Institute of Basic Biological Problems, Russian Academy of Sciences, ul. Institutskaya 2, Pushchino, Moscow oblast, 142290, Russia
2. Shemyakin_Ovchinnikov Institute of Bioorganic Chemistry (Pushchino Branch), Russian Academy of Sciences, pr. Nauki 6, Pushchino, Moscow oblast, 142290, Russia
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| Abstract: | The polyacrylamide gel electrophoresis of chernozem humic acids (HAs) followed by ultraviolet detection (λ = 312 nm) has revealed a new highly fluorescent fraction that has the highest electrophoretic mobility and the lowest nominal molecular weight (NMW). The preparative isolation of the fraction has been performed using the multiple microfiltration of the same HA sample in a 7 M carbamide solution on a membrane with a nominal pore size of 5 kDa. Thirty ultrafiltrates with NMW < 5 kDa and different fluorescence maximums in the region of 475–505 nm have been prepared, as well as a nonfluorescent concentrate with NMW > 5 kDa. Fluorescence maximums at and below 490 nm have been noted only in the first four ultrafiltrates. All the ultrafiltrates have been combined into the fraction with NMW < 5 kDa, which has been successively passed through membranes of 3 and 1 kDa. Solutions of subfractions F 3–5 kDa, F 1–3 kDa, and F < 1 kDa with fluorescence maximums at 505, 488, and 465 nm, respectively, have been prepared. The F < 1 kDa subfraction with the lowest NMW had the highest fluorescence intensity. The distribution of the fluorescence maximums in the ultrafiltrates has indicated the presence of at least two groups of fluorophores and has confirmed the supramolecular organization of the extracted soil HAs. |
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