A conserved motif flags acyl carrier proteins for β-branching in polyketide synthesis

Type I PKSs often utilise programmed β-branching, via enzymes of an “HMG-CoA synthase (HCS) cassette”, to incorporate various side chains at the second carbon from the terminal carboxylic acid of growing polyketide backbones. We identified a strong sequence motif in Acyl Carrier Proteins (ACPs) where β-branching is known. Substituting ACPs confirmed a correlation of ACP type with β-branching specificity. While these ACPs often occur in tandem, NMR analysis of tandem β-branching ACPs indicated no ACP-ACP synergistic effects and revealed that the conserved sequence motif forms an internal core rather than an exposed patch. Modelling and mutagenesis identified ACP Helix III as a probable anchor point of the ACP-HCS complex whose position is determined by the core. Mutating the core affects ACP functionality while ACP-HCS interface substitutions modulate system specificity. Our method for predicting β-carbon branching expands the potential for engineering novel polyketides and lays a basis for determining specificity rules

Throughput, Delay and Power Losses in Bus-Oriented Optical Networks with Multiple Transmitters and Receivers per Station

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryAT&T Bell LaboratoriesU of I OnlyRestricted to UIUC communit

Throughput, Delay and Power Losses in Bus-Oriented Optical Networks with Multiple Transmitters and Receivers per Station

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryAT&T Bell LaboratoriesU of I OnlyRestricted to UIUC communit

Multi-scale modeling of anisotropic polycrystalline plasticity in a shaped charged liner

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (leaves 70-73).by Matthew J. Busche.S.M

Optimal Play of the Farkle Dice Game

We present and solve optimality equations for the 2-player, jeopardy dice game Farkle (a.k.a. Dix Mille, Ten Thousand). For fairest play, we recommend 200 compensation points at the beginning of the game for the second player. We then compute the strategy that maximizes expected score, demonstrate a means for replicating such play with mental mathematics, and augment this method so as to enable human Farkle play against which complex optimal play maintains only a small win advantage of ~1.7754%

Contactless nonlinear optics mediated by long-range Rydberg interactions

In conventional nonlinear optics, linear quantum optics1, 2, and cavity quantum electrodynamics3, 4 to create effective photon–photon interactions photons must have, at one time, interacted with matter inside a common medium. In contrast, in Rydberg quantum optics5, 6, 7, 8, 9, 10, optical photons are coherently and reversibly mapped onto collective atomic Rydberg excitations11, giving rise to dipole-mediated effective photon–photon interactions that are long range12, 13. Consequently, a spatial overlap between the light modes is no longer required. We demonstrate such a contactless coupling between photons stored as collective Rydberg excitations in spatially separate optical media. The potential induced by each photon modifies the retrieval mode of its neighbour7, 9, 14, 15, leading to correlations between them. We measure these correlations as a function of interaction strength, distance and storage time, demonstrating an effective interaction between photons separated by 15 times their wavelength. Contactless effective photon–photon interactions16 are relevant for scalable multichannel photonic devices15, 17 and the study of strongly correlated many-body dynamics using light18