Dipole–dipole interaction and the relative stability of different types of aggregates of helical polypeptides

π–π Interlocking Effect for Designing Biodegradable Nanorods with Controlled Lateral Surface Curvature

“…47−50 With the introduction of a poor solvent, these HTT chains further aggregate under the side-by-side antiparallel (SSA) arrangement (Scheme S1C) and also due to the permanent dipole moments. 51 Assuming that the HTT aggregates remain strictly straight during the SSA process, nanorods with a quite straight lateral surface could be theoretically predicted (Scheme S1D).…”

“…Polypeptides are promising candidates for biomedical applications due to their close affiliation to proteins. − Compared to other degradable polymers, polypeptides feature various secondary structures, including α-helices and β-sheets. − This feature has a huge impact on their self-assembly behavior. ,− Poly-γ-benzyl- l -glutamate (PBLG) is a particularly interesting polypeptide that adopts the head-to-tail (HTT) arrangement in helicogenic solvents (such as dioxane, ethylene dichloride, and chloroform) because each α-helical PBLG molecule has a permanent dipole moment along the direction of its rod axis (Scheme S1A,B). − With the introduction of a poor solvent, these HTT chains further aggregate under the side-by-side antiparallel (SSA) arrangement (Scheme S1C) and also due to the permanent dipole moments . Assuming that the HTT aggregates remain strictly straight during the SSA process, nanorods with a quite straight lateral surface could be theoretically predicted (Scheme S1D).…”

Conformal transition of form II to form I in poly(L‐proline) and the aggregation of form I. I. Acetic acid–propanol solvent system

“…Many studies for intermolecular aggregation of polypeptides in organic solvents have been c o n d~c t e d , l~-~~ and it was found that head-to-tail and side-by-side (antiparallel) arrangements O C C U T .~~-~~ Although the criterion for the occurrence of the two types of aggregations is not known precisely, it is commonly found that the side-by-side type aggregation occurs mainly in stiff low molecular weight samples,22 but the head-to-tail type aggregation via some specific interaction between end-groups is found in high molecular weight compounds. 21 In the present study, we used a higher molecular weight PLP sample [ M u = 31,000 (in acetic acid)] than Cam et al's samples14 [ M , = 19,500 and M, = 13,800 (both in propionic acid)]. It was found that the head-to-tail type of aggregation occurs in contrast to Carr et al's report.…”

Polarizability of Rigid Rod Macromolecules with Dipolar Side Chains. A Nonlinear Dielectric Effect Study

“…For the solutions examined, one determines the moment of the aggregates, depending upon their structure, about which not much is known. However, the polarizability can be discussed satisfactorily, as it is not influenced by the unknown directions of molecular axes oriented side by side within the associates of high molecular weight PBLG.33, 35 The microwave absorption found by Davies et al in PBLG solutions28 can also be attributed to cooperative side group motions. The absorption intensity corresponds to a free rotation of dipoles of 9.0 X 10~3°Cm for PBLG of mol wt 110000 in dioxane, as compared with 15.0 X 10"30 Cm from our dielectric data for the sample of similar molecular weight, both markedly higher than the moment of a single group of 6.0 X 10~3°Cm.…”