Growth conditions of F9 embryonal carcinoma cells affect the degree of DNA methylation

We have investigated differences in C * pG methylation between F9 embryonal carcinoma cells in vitro and as tumor cells grown in vivo using Msp I and Hpa II restriction isoschizomers. Southerns were hybridized with two low copy number probes, mouse major β-globin (f7) and a class I, histocompatibility-2 cDNA clone (pH-2 d -4). In each case, the tumor-DNA was hypomethylated while the DNA from F9 cells grown in vitro was moderately methylated. We conclude that growth conditions or cell-cell interactions can greatly affect methylation of C * pG sites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43248/1/11033_2004_Article_BF00776983.pd

Automated extraction of single H atoms with STM: tip state dependency

The atomistic structure of the tip apex plays a crucial role in performing reliable atomic-scale surface and adsorbate manipulation using scanning probe techniques. We have developed an automated extraction routine for controlled removal of single hydrogen atoms from the H:Si(100) surface. The set of atomic extraction protocols detect a variety of desorption events during scanning tunneling microscope (STM)-induced modification of the hydrogen-passivated surface. The influence of the tip state on the probability for hydrogen removal was examined by comparing the desorption efficiency for various classifications of STM topographs (rows, dimers, atoms, etc). We find that dimer-row-resolving tip apices extract hydrogen atoms most readily and reliably (and with least spurious desorption), while tip states which provide atomic resolution counter-intuitively have a lower probability for single H atom removal

On the exchange of intersection and supremum of sigma-fields in filtering theory

We construct a stationary Markov process with trivial tail sigma-field and a nondegenerate observation process such that the corresponding nonlinear filtering process is not uniquely ergodic. This settles in the negative a conjecture of the author in the ergodic theory of nonlinear filters arising from an erroneous proof in the classic paper of H. Kunita (1971), wherein an exchange of intersection and supremum of sigma-fields is taken for granted.Comment: 20 page

Unique determination of “subatomic” contrast by imaging covalent backbonding

The origin of so-called “subatomic” resolution in dynamic force microscopy has remained controversial since its first observation in 2000. A number of detailed experimental and theoretical studies have identified different possible physicochemical mechanisms potentially giving rise to subatomic contrast. In this study, for the first time we are able to assign the origin of a specific instance of subatomic contrast as being due to the back bonding of a surface atom in the tip−sample junction

On-Surface Covalent Linking of Organic Building Blocks on a Bulk Insulator

Kittelmann M, Rahe P, Nimmrich M, Hauke CM, Gourdon A, Kühnle A. On-Surface Covalent Linking of Organic Building Blocks on a Bulk Insulator. ACS Nano. 2011;5(10):8420-8425.On-surface synthesis in ultrahigh vacuum provides a promising strategy for creating thermally and chemically stable molecular structures at surfaces. The two-dimensional confinement of the educts, the possibility of working at higher (or lower) temperatures in the absence of solvent, and the templating effect of the surface bear the potential of preparing compounds that cannot be obtained in solution. Moreover, covalently linked conjugated molecules allow for efficient electron transport and are, thus, particularly interesting for future molecular electronics applications. When having these applications in mind, electrically insulating substrates are mandatory to provide sufficient decoupling of the molecular structure from the substrate surface. So far, however, on-surface synthesis has been achieved only on metallic substrates. Here we demonstrate the covalent linking of organic molecules on a bulk insulator, namely, calcite. We deliberately employ the strong electrostatic interaction between the carboxylate groups of halide-substituted benzoic adds and the surface calcium cations to prevent molecular desorption and to reach homolytic cleavage temperatures. This allows for the formation of aryl radicals and intermolecular coupling. By varying the number and position of the halide substitution, we rationally design the resulting structures, revealing straight lines, zigzag structures, and dimers, thus providing clear evidence for the covalent linking. Our results constitute an important step toward exploiting on-surface synthesis for molecular electronics and optics applications, which require electrically insulating rather than metallic supporting substrates

A koherencia mint a lelki és testi egészség alapvető meghatározója a mai magyar társadalomban = Sense of coherence as an important determinant of mental and physical health

Az ún. salutogenezis modell olyan keretet kínál, amelyben a koherencia élmény bevezetésével lehetőség nyílik az „egész”-ség dinamikus értelmezésére. Vizsgálatunkban a Richard Rahe-féle, az „élet értelme” koherencia kérdőív összefüggéseit vizsgáltuk az egészségi állapottal. A Hungarostudy 2002 felmérés a 18 évesnél idősebb magyar népességet életkor, nem és terület szerint képviseli. 12 640 személlyel vettünk fel otthoni interjút. Az így vizsgált koherencia mutatót az egészségi állapot igen fontos előrejelzőjének találtuk. Ha az adatokat életkor, nem és iskolázottság szerint korrigáltuk, az egészségi állapot önbecslése mintegy 10-szer, a munkaképesség 8-szor jobb, a depresszió valószínűsége 7-szer alacsonyabb volt. Az „élet értelme” mutató igen szoros kapcsolatban áll az önhatékonysággal, a problémaorientált megbirkózással, a társas támogatással, ezzel szemben kevésbé függ az iskolázottságtól, az életkortól és a nemtől

Kinetic control of molecular assembly on surfaces

It is usually assumed that molecules deposited on surfaces assume the most thermodynamically stable structure. Here we show, by considering a model system of dihydroxybenzoic acid molecules on the (10.4) surface of calcite, that metastable molecular architectures may also be accessed by choosing a suitable initial state of the molecules which defines the observed transformation path. Moreover, we demonstrate that the latter is entirely controlled by kinetics rather than thermodynamics. We argue that molecules are deposited as dimers that undergo, upon increase of temperature, a series of structural transitions from clusters to ordered striped and then dense networks, and finally to a disordered structure. Combining high-resolution dynamic atomic force microscopy experiments and density-functional theory calculations, we provide a comprehensive analysis of the fundamental principles driving this sequence of transitions. Our study may open new avenues based on kinetic control as a promising strategy for achieving tailored molecular architectures on surfaces

Visualizing the orientational dependence of an intermolecular potential

Scanning probe microscopy can now be used to map the properties of single molecules with intramolecular precision by functionalization of the apex of the scanning probe tip with a single atom or molecule. Here we report on the mapping of the three-dimensional potential between fullerene (C₆₀) molecules in different relative orientations, with sub-Angstrom resolution, using dynamic force microscopy (DFM). We introduce a visualization method which is capable of directly imaging the variation in equilibrium binding energy of different molecular orientations. We model the interaction using both a simple approach based around analytical Lennard–Jones potentials, and with dispersion-force-corrected density functional theory (DFT), and show that the positional variation in the binding energy between the molecules is dominated by the onset of repulsive interactions. Our modelling suggests that variations in the dispersion interaction are masked by repulsive interactions even at displacements significantly larger than the equilibrium intermolecular separation