25Scanning probe microscopy has been used in biol ogy for a relatively long time, and considerable experi ence with this technique has been accumulated [1][2][3][4]. Certain achievements here are unique: they reach the level of art and are quite rightfully presented in refer ence works [5]. Our task is to expand the use of scan ning probe microscopy for a more widespread and inexpensive investigation of biopolymer molecules in an air atmosphere. However, the presence of water vapors in the atmosphere leads to coating of biomole cules by an adsorbate composed mostly of water. Moreover, the hydrophilic nature of biomolecules results in coating of the molecules exposed to atmo spheric air by a dense film of bound water [6]; the thickness of this film on the surface of solid objects is close to 1 nm [7]. On one hand, this causes consider able difficulties for the retrieval of information about individual fragments of the molecule (the useful infor mative signal is very weak); on the other hand, the presence of adsorbate allows for implementation of the tunneling mode in the more feasible nanoamper current range for the possible subsequent identifica tion of the fragments.Standard procedures of scanning tunnel micros copy (STM) described in user manuals and mono graphs [8] do not provide for a sufficiently high resolu tion for the imaging of polymer molecule fragments. The model concepts for scanning and processing of STM images outlined in the present article allow for production of digital figurative images of nanometer Abbreviations: STM-scanning tunneling microscopy. sized objects (for example, fragments of polymer mol ecules) with characteristic distinguishing features. On one hand, this approach does not require imaging the molecular surface with atomic resolution that is very labor consuming, especially in the atmosphere of air; on the other hand, it yields rather complete and useful information on the fragment sequence of macromole cules, such as biopolymers. MODEL CONCEPTS USED TO OBTAIN A FIGURATIVE IMAGE OF A MOLECULEA figurative image of a nanometer sized object refers to the topography of the object differing from that of the actual one, but conserving the distinctive features.Our analysis will be based on a simple formula for tunneling current between two electrodes used in most manuals and textbooks on scanning tunneling micros copy [8]. The influence of atmospheric air will be taken into account in the following way:(1)where d is the interelectrode gap; V is the voltage applied (V = const); R 0t is the resistance value during a short circuit when d = 0; k t = (ប is Planck's constant; m and q are the mass and charge of an elec tron, respectively; and = (ϕ 1 + ϕ 2 )/2 is the average MOLECULAR BIOPHYSICSAbstract-Images of the sequence of fragments of a biopolymer molecule have been obtained using scanning tunneling microscopy under native conditions (air atmosphere) with bacterial DNA as the model object. Air adsorbate (mostly formed by water vapors) coating the molecules increases the local tunnel conduc...

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