Real Options under Choquet-Brownian Ambiguitys

Real options models characterized by the presence of “ambiguity” (or “Knightian uncertainty”) have been recently proposed. But based on recursive multiple-priors preferences, they typically describe ambiguity through a range of Geometric Brownian motions and solve it by application of a maxmin expected utility criterion among them (worst case). This reduces acceptable individual preferences to the single case of an extreme form of pessimism. In contrast, by relying on dynamically consistent “Choquet-Brownian” motions to represent the ambiguous cash flows expected from a project, we show that a much broader spectrum of attitudes towards ambiguity may be accounted for, improving the explanatory and application potentials of these appealing expanded real options models. In the case of a perpetual real option to invest, ambiguity aversion may delay the moment of exercise of the option, while the opposite holds true for an ambiguity seeking decision maker. Furthermore, an intricate relationship between risk and ambiguity appears strikingly in our model.

Real Options under Choquet-Brownian Ambiguity

Real options models characterized by the presence of ambiguity have been recently proposed. But based on recursive multiple-priors approaches to solve ambiguity, these seminal models reduce individual preferences to extreme pessimism by considering only the worst case scenario. In contrast, by relying on dynamically consistent Choquet-Brownian motions to model the dynamics of ambiguous expected cash flows, we show that a much broader spectrum of attitudes towards ambiguity may be accounted for. In the case of a perpetual real option to invest, ambiguity aversion delays the moment of exercise of the option, while the opposite holds true for an ambiguity lover.Real Options; Ambiguity; Irreversible investment; Optimal stopping; Knightian uncertainty; Choquet-Brownian motions

Real Options under Choquet-Brownian Ambiguity

Real options models characterized by the presence of ambiguity have been recently proposed. But based on recursive multiple-priors approaches to solve ambiguity, these seminal models reduce individual preferences to extreme pessimism by considering only the worst case scenario. In contrast, by relying on dynamically consistent Choquet-Brownian motions to model the dynamics of ambiguous expected cash flows, we show that a much broader spectrum of attitudes towards ambiguity may be accounted for. In the case of a perpetual real option to invest, ambiguity aversion delays the moment of exercise of the option, while the opposite holds true for an ambiguity lover

The NTPase activity of the double FYVE domain-containing protein 1 regulates lipid droplet metabolism.

Lipid droplets (LDs) are transient lipid storage organelles that can be readily tapped to resupply cells with energy or lipid building blocks and therefore play a central role in cellular metabolism. However, the molecular factors and underlying mechanisms that regulate the growth and degradation of LDs are poorly understood. It has emerged that proteins that establish contacts between LDs and the endoplasmic reticulum play a critical role in regulating LD metabolism. Recently, the autophagy-related protein, double FYVE domain-containing protein 1 (DFCP1/ZFYVE1) was shown to reside at the interface of the endoplasmic reticulum and LDs, however, little is known about the involvement of DFCP1 in autophagy and LD metabolism. Here, we show that DFCP1 is a novel NTPase that regulates free fatty acid metabolism. Specifically, we show that DFPC1-knockdown, particularly during starvation, increases cellular free fatty acids and decreases the levels of cellular TAGs, resulting in accumulated small LDs. Using selective truncations, we demonstrate that DFCP1 accumulation on LDs in cells and in vitro is regulated by a previously unknown NTPase domain. Using spectroscopic approaches, we show that this NTPase domain can dimerize and can hydrolyze both ATP and GTP. Furthermore, mutations in DFCP1 that either impact nucleotide hydrolysis or dimerization result in changes in the accumulation of DFCP1 on LDs, changes in LD density and size, and colocalization of LDs to autophagosomes. Collectively, our findings suggest that DFCP1 is an NTPase that modulates the metabolism of LDs in cells

Efficient introduction of aryl bromide functionality into proteins in vivo

Artificial proteins can be engineered to exhibit interesting solid state, liquid crystal or interfacial properties and may ultimately serve as important alternatives to conventional polymeric materials. The utility of protein-based materials is limited, however, by the availability of just the 20 amino acids that are normally recognized and utilized by biological systems; many desirable functional groups cannot be incorporated directly into proteins by biosynthetic means. In this study, we incorporate para-bromophenylalanine (p-Br-phe) into a model target protein, mouse dihydrofolate reductase (DHFR), by using a bacterial phenylalanyl-tRNA synthetase (PheRS) variant with relaxed substrate specificity. Coexpression of the mutant PheRS and DHFR in a phenylalanine auxotrophic Escherichia coli host strain grown in p-Br-phe-supplemented minimal medium resulted in 88% replacement of phenylalanine residues by p-Br-phe; variation in the relative amounts of phe and p-Br-phe in the medium allows control of the degree of substitution by the analog. Protein expression yields of 20–25 mg/l were obtained from cultures supplemented with p-Br-phe; this corresponds to about two-thirds of the expression levels characteristic of cultures supplemented with phe. The aryl bromide function is stable under the conditions used to purify DHFR and creates new opportunities for post-translational derivatization of brominated proteins via metal-catalyzed coupling reactions. In addition, bromination may be useful in X-ray studies of proteins via the multiwavelength anomalous diffraction (MAD) technique

Corporate financing decisions under ambiguity : pecking order and liquidity policy implications

This paper addresses the following unresolved questions fromthe perspective of ambiguity theory: Why do some firms issue equity instead of debt?Why did most firms retain their cash holdings instead of distributing themas dividends in recent times? How do firms change their financing policies during a period of severe financial constraints and ambiguity, orwhen facing the threat of an unpredictable financial crisis? We analyze how the values of the firm's equity and debt are affected by ambiguity. Wealso showthat cash holdings are retained longer if the investors' ambiguity aversion bias is sufficiently large,while cash holdings become less attractivewhen the combined impact of ambiguity and ambiguity aversion is relatively low

Evaluation of log P, pKa, and log D predictions from the SAMPL7 blind challenge

The Statistical Assessment of Modeling of Proteins and Ligands (SAMPL) challenges focuses the computational modeling community on areas in need of improvement for rational drug design. The SAMPL7 physical property challenge dealt with prediction of octanol-water partition coefficients and pKa for 22 compounds. The dataset was composed of a series of N-acylsulfonamides and related bioisosteres. 17 research groups participated in the log P challenge, submitting 33 blind submissions total. For the pKa challenge, 7 different groups participated, submitting 9 blind submissions in total. Overall, the accuracy of octanol-water log P predictions in the SAMPL7 challenge was lower than octanol-water log P predictions in SAMPL6, likely due to a more diverse dataset. Compared to the SAMPL6 pKa challenge, accuracy remains unchanged in SAMPL7. Interestingly, here, though macroscopic pKa values were often predicted with reasonable accuracy, there was dramatically more disagreement among participants as to which microscopic transitions produced these values (with methods often disagreeing even as to the sign of the free energy change associated with certain transitions), indicating far more work needs to be done on pKa prediction methods