Abstract
The chemical and physical properties of glass do not allow it to be considered as an inert material. Therefore, it is necessary to discuss the ability of laboratory glassware to influence the state and properties of aqueous solutions, including DNA solutions. As a demonstration of this ability, it is shown here how contact with glass affects the state of salts in aqueous solutions. In terms of the topic under discussion, it is especially important that sodium salts are very sensitive to these contacts. Thus, it is shown here that contact with glass can affect the formation of fibers from sodium salts of DNA, which were mainly used in X-ray studies aimed at determining the molecular structure and parameters of DNA molecules. Special attention is paid to the fact that laboratory glassware is also sensitive to contact with aqueous solutions, including DNA solutions. That such sensitivity may be important to biologists is also shown here. In particular, it was shown how ignoring the sensitivity of silica glass, from which the photometric cells are made, to electrization gave rise to misconceptions about the spectral properties of aqueous solutions, including DNA solutions. The effect of air dissolved in aqueous DNA solutions on the spectral properties of both these solutions and the photometric cells containing them is also shown. In particular, it was shown that UV absorption of aqueous DNA solutions, which does not contain air, is completely insensitive to heating, and UV absorption of aqueous DNA solutions, which are saturated with air, is supersensitive to heating. In other words, it is shown here that our understanding of the thermal denaturation of DNA, which is reflected in the UV absorption of its aqueous solutions, was formed due to these two types of sensitivity. In the end, a conclusion is proposed here about the significant contribution of glass and air to the creation of traditional ideas about the structure and properties of DNA.
Highlights
It has long been known that glass is capable of absorbing electrons, thereby suppressing chemical reactions between free radicals, in particular-chain reactions occurring by a free radical mechanism
It is useful to make sure once again that highly visible fibers are formed in aqueous solutions of salts in contact with the glass surface (Figure 3)
Numerous filaments that form on the surface of silica gel from an aqueous solution of NaCl (Figure 4), suggest that this assumption corresponds to reality
Summary
It has long been known that glass is capable of absorbing electrons, thereby suppressing chemical reactions between free radicals, in particular-chain reactions occurring by a free radical mechanism. The walls of laboratory glassware are able to absorb electrons that are part of chemically active molecules and atoms of hydrogen and oxygen (H* + glass wall → inactive H, and O2* + glass wall → inactive O2) and stop their interaction, preventing the combustion of hydrogen gas in an oxygen atmosphere. For this reason, glassware is traditionally considered to be an inhibitor of free radical chemical reactions [1, 2]. The spiral (!) filaments appearing in aqueous solutions of salts near the walls of glassware (Figure 1) [4] clearly show both the existence of this field and its shape-forming action
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