The role of molecular structure, charge, and hydrophobicity in polyelectrolyte layer-by-layer assembly (LbL) of thin films has been studied using the model polypeptides poly-L-glutamatic acid (PLGA) and poly-L-lysine (PLL), quartz crystal microbalance (QCM), and circular dichroism spectroscopy (CD). The adsorption behavior of PLGA and PLL has been compared with the structure of these molecules in aqueous solution under the same conditions. The data show that the deposition of polypeptide per adsorption step scales with average secondary structure content, whether alpha helix or beta sheet. This is contrary to the expectation based on the view that hydrogen bonds are crucial to polypeptide film assembly, because secondary structure formation in a polypeptide reduces its intermolecular hydrogen-bonding potential. The data also show that polypeptide adsorption scales with ionic strength and chain length. Taken together, the results increase knowledge of polypeptide-based LbL thin film fabrication and will help to provide a firmer foundation for the use of natural or designed polypeptides in LbL.
We introduce a new measurable quantity, $R_{\Delta \phi}$, for studies of the
rapidity and transverse momentum dependence of dijet azimuthal decorrelations
in hadron-hadron collisions. In pQCD, $R_{\Delta \phi}$ is computed as a ratio
of three-jet and dijet cross sections in which the parton distribution
functions cancel to a large extent. At the leading order, $R_{\Delta \phi}$ is
proportional to $\alpha_s$, and the transverse momentum dependence of can
therefore be exploited to determine $\alpha_s$. We compute the NLO pQCD theory
predictions and non-perturbative corrections for $R_{\Delta \phi}$ at the LHC
and the Tevatron and investigate the corresponding uncertainties. From this, we
estimate the theory uncertainties for $\alpha_s$ determinations based on
$R_{\Delta \phi}$ at both colliders. The potential of $R_{\Delta \phi}$
measurements for tuning Monte Carlo event generators is also demonstrated.Comment: 20 pages, 11 figures, 1 table, submitted to JHE
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