and performances of nanodevices highly depend on the shape and quality of 2D materials, [5] various routes have been explored to synthesize high-quality controllable-shaped 2D materials. This has led to the development of different synthesis methods including mechanical exfoliation, [6] liquid-phased exfoliation, [7] and chemical vapor deposition (CVD). [8] CVD has been shown to be the most performant synthetic method, and is currently the most widely used for large-scale fabrication of high-quality 2D materials. [9] Tremendous efforts have been made to control the CVD synthetic process, for example, growing large single crystals of graphene by limiting the growth process to one nucleus, [10] fabricating wafer-scale single crystals of h-BN on liquid-gold substrates, [11] or depositing 2D transitionmetal chalcogenides via adding molten salt. [12] However, to achieve the precise control of the growth process of 2D materials, it is essential to take into account its underlying physical mechanisms. Many attempts have been made to explore the atomic mechanism and grow higher-quality materials by considering the oxygen effect, [13] the hydrogen etching, [14] the edgeenergy equilibrium, [15] the classical Wulff structure, [16] and the phase-field approach in the past years. [17] However, due to a large number of influenced factors and the underlying intricate nanoscale physical mechanisms, the precise control of the shape and quality of CVD-grown 2D materials, till now, is still regarded as a formidable challenge.Our study shows that dendritic-structured patterns commonly appear during the CVD growth processes of various 2D materials. To understand this phenomenon, we investigate the growth mechanisms in the framework of the fractal theory. [18] Although, in the past, this theory has provided an explanation for the sound of irregular or fragmented natural structures and self-similar patterns with the unfolding symmetry, [19] this theory has never been applied, to our knowledge, to the interpretation of growth mechanisms of CVD-grown 2D materials. Here, we demonstrate, both experimentally and theoretically, the existence of fractal growth mechanisms in the CVD growth process of graphene, h-BN, and molybdenum disulfide (MoS 2 ). Based on the classic diffusion-limited aggregation (DLA), [20] a typical model of the fractal theory, we develop an The precise control of the shape and quality of 2D materials during chemical vapor deposition (CVD) processes remains a challenging task, due to a lack of understanding of their underlying growth mechanisms. The existence of a fractal-growth-based mechanism in the CVD synthesis of several 2D materials is revealed, to which a modified traditional fractal theory is applied in order to build a 2D diffusion-limited aggregation (2D-DLA) model based on an atomic-scale growth mechanism. The strength of this model is validated by the perfect correlation between theoretically simulated data, predicted by 2D-DLA, and experimental results obtained from the CVD synthesis of graphene, hexagonal b...

The effects of bases flanking single bulky lesions derived from the binding of a benzo[a]pyrene 7,8-diol 9,10-epoxide derivative ((+)-7R,8S,9S,10R stereoisomer) to N(2)-guanine (G*) on translesion bypass catalyzed by the Y-family polymerase pol kappa (hDinB1) were examined in vitro. The lesions were positioned near the middle of six different 43-mer 5'-...XG*Y... sequences (X, Y = C, T, or G, with all other bases remaining fixed). The complementary dCTP is preferentially inserted opposite G* in all of the sequences; however, the proportions of other dNTPs inserted varies as a function of X and Y. The dCTP insertion efficiencies, f(ins) = (V(max)/K(m))(ins), are smaller in the XG*Y than in XGY sequences by factors of approximately 50-90 (GG*T and GG*C) or 5000-25000 (TG*G and CG*G). Remarkably, in XG*Y sequences, f(ins) varies by as much as 3 orders of magnitude, being smallest with G flanking the lesions on the 3'-side and highest with G flanking the adducts on the 5'-side. One-step primer extension efficiencies just beyond the lesions (f(ext)) are generally smaller than f(ins) and also depend on base sequence. However, reasonably efficient translesion bypass of the (+)-trans-[BP]-N(2)-dG adducts is observed in all sequences in running-start experiments with full, or nearly full, primer extension being observed under conditions of [dNTP] > K(m). The key features here are the relatively robust values of the kinetic parameters V(max) that are either diminished to a moderate extent or even enhanced in the presence of the (+)-trans-[BP]-N(2)-dG adducts. In contrast to the small effects of the lesions on V(max), the apparent K(m) values are orders of magnitude greater in XG*Y than in the unmodified XGY sequences. Thus the bypass of (+)-trans-[BP]-N(2)-dG adducts under conditions when [dNTP] < K(m) is quite inefficient. These considerations may be of importance in vivo where [dNTP]

For many years, the concept that the heparin-binding sequence is sequestered within vitronectin and exposed upon denaturation of the protein has guided experimental design and interpretation of related structurefunction studies on the protein. Within the circulation, complicated networks of interactions between proteins and other macromolecules are important for maintaining stasis. An example of the complex interplay that must exist among these biomolecules is provided by the human glycoprotein, vitronectin. Vitronectin interacts with a wide variety of ligands that are involved in control of diverse physiological processes including coagulation, fibrinolysis, tumor metastasis, the humoral immune response, and cellular migration (reviewed in Refs. 1-6). A partial list of target macromolecules that interact with vitronectin includes heparin, collagen, plasminogen, plasminogen activator inhibitor-1, serine protease inhibitor-protease complexes, and a subclass of integrin receptors on the surface of cells.Indeed, one of the first molecules shown to interact with vitronectin was heparin (7-11), and this interaction has since been widely investigated (12-16). Much of the early work on vitronectin was devoted to evaluating structural requirements for heparin binding, including tests of the effects of denaturation or proteolysis of vitronectin on heparin binding activity. Binding activity was evaluated from vitronectin interactions with a heparin column, estimated in terms of the salt concentrations required to elute bound vitronectin. From these studies came a most striking observation: vitronectin binding to heparin was enhanced upon treatment of the protein with urea, heat, or acid (9). This phenomenon was exploited by Yatohgo et al. (17) to develop an affinity-based purification scheme for vitronectin that invoked chemical denaturation of bulk plasma prior to chromatography on heparin-agarose. As early as 1984, a model emerged in which the heparin-binding region is buried within the native molecule, so that heparin binding is induced when this cryptic binding site is exposed upon denaturation of vitronectin (11,16). This model has been generally accepted, and more recent work has included attempts to correlate the heparin binding properties of native and denatured/renatured vitronectin with other functions of the protein (12, 18 -27). The two forms of the protein, which are sometimes denoted the "non-heparin-binding" (native) and "heparin-binding" (denatured/renatured) species, are characterized in much of the ongoing work in the field.Many years after the initial work examining effects of denaturation on vitronectin, it was recognized that denaturation is accompanied by self-association of the protein into a multimeric form (28,29). Multimerization of vitronectin ensues following unfolding of the protein to a structurally altered form that can be detected with a variety of conformationally sensitive monoclonal antibodies (29 -31). This partially folded intermediate form has a high propensity to self-associate int...