(ii) a trigger that controls autocatalytic growth; and (iii) inhibitory processes that remove activating thiol species produced during the autocatalytic cycle. In contrast to previous studies demonstrating oscillations and bistability using highly evolved biomolecules (i.e., enzymes 15 and DNA 16,17 ) or inorganic molecules of questionable biochemical relevance (e.g. those used in Belousov-Zhabotinsky-type reactions), 18,19 the organic molecules used in our network are relevant to current metabolism and similar to those that might have existed on early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable, and oscillatory behavior, we identified principles that clarify how dynamic networks relevant to life might possibly have developed. In the future, modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks, and of synthetic self-regulating and evolving chemical systems.3 Figure 1 summarizes the network of organic reactions that we used to assemble our model system. All of these reactions are nearly quantitative, and the structure of their reactants can be varied by synthesis to control rates of reactions. Thiols and thioesters, which are central to these reactions, are important in many biological processes (e.g., the formation of disulfide bonds in proteins, transformations involving coenzyme-A, the reduction of oxidized molecules by glutathione, 20 the synthesis of polyketides, 21 and the nonribosomal synthesis of peptides 21 ), and thus, might represent reactions that enabled life to emerge on early Earth. 22 To control the dynamics of these processes, we constructed a modular chemical reaction network (CRN) shown schematically in control-theoretic terms 23 in Fig. 1a. A "trigger" produces an initial chemical signal, and an "auto-amplifier" amplifies this signal, which may or may not be suppressed by inhibition. To keep the reactions out of equilibrium-and thus, to enable the self-organization of reactions by communication through concentrations of reactants and products -we used a continuous-stirred tank reactor (CSTR) to mix reactants and products, while allowing a flux of species into and out of the network over time. A biological cell has some conceptual analogies to a micron-scale, diffusively mixed, tank reactor. The dynamic behavior of this system -especially bistability and oscillationsreflects the balances of triggering, auto-amplification, and inhibition.We first constructed a chemical network capable of auto-amplification using thiols and thioesters (Fig. 1b). The starting components of the network are cystamine (CSSC, 3) and L-alanine ethyl thioester (AlaSEt, 2). Trace amounts of cysteamine (CSH, 1) are generated as follows: AlaSEt slowly hydrolyzes, generating alanine (8) and ethanethiol (ESH, 4); EtSH then reacts with CSSC via thiolate-disulfide interchange, 24 yielding disulfide 6 and CSH. With CSH present, self-amplification oc...

We report a novel method for the synthesis of a self-reducible (thermally reducible without a reducing atmosphere) and alcohol-soluble copper-based metal-organic decomposition (MOD) ink for printed electronics. Alcohol-solvent-based conductive inks are necessary for commercial printing processes such as reverse offset printing. We selected copper(II) formate as a precursor and alkanolamine (2-amino-2-methyl-1-propanol) as a ligand to make an alcohol-solvent-based conductive ink and to assist in the reduction reaction of copper(II) formate. In addition, a co-complexing agent (octylamine) and a sintering helper (hexanoic acid) were introduced to improve the metallic copper film. The specific resistivity of copper-based MOD ink (Cuf-AMP-OH ink) after heat treatment at 350 °C is 9.46 μΩ·cm, which is 5.5 times higher than the specific resistivity of bulk copper. A simple stamping transfer was conducted to demonstrate the potential of our ink for commercial printing processes.

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Biomolecular recognition can be stubborn; changes in the structures of associating molecules, or the environments in which they associate, often yield compensating changes in enthalpies and entropies of binding and no net change in affinities. This phenomenon-termed enthalpy/entropy (H/S) compensation-hinders efforts in biomolecular design, and its incidence-often a surprise to experimentalists-makes interactions between biomolecules difficult to predict. Although characterizing H/S compensation requires experimental care, it is unquestionably a real phenomenon that has, from an engineering perspective, useful physical origins. Studying H/S compensation can help illuminate the still-murky roles of water and dynamics in biomolecular recognition and self-assembly. This review summarizes known sources of H/ S compensation (real and perceived) and lays out a conceptual framework for understanding and dissecting-and, perhaps, avoiding or exploiting-this phenomenon in biophysical systems.

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