Molecular Packing in Cylindrical Micelles

2007 ◽  
pp. 41-79 ◽  
Author(s):  
Avinoam Ben-Shaul ◽  
Sylvio May
Keyword(s):  
Molecular Packing ◽  
Cylindrical Micelles

Molecular Packing in Cylindrical Micelles

2007 ◽  
pp. 41-80 ◽  
Author(s):  
Sylvio May ◽  
Avinoam Ben-Shaul
Keyword(s):  
Molecular Packing ◽  
Cylindrical Micelles

Structure and Dynamics of Spherical and Rodlike Alkyl Ethoxylate Surfactant Micelles Investigated Using NMR Relaxation and Atomistic Molecular Dynamics Simulations

2019 ◽  
Author(s):  
Allison Edwards ◽  
Abdolreza Javidialesaadi ◽  
Katie Weigandt ◽  
George Stan ◽  
Charles Eads
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nmr Relaxation ◽  
Cross Relaxation ◽  
Relaxation Rates ◽  
Surfactant Micelles ◽  
Cylindrical Micelles ◽  
Spherical Micelles ◽  
Dynamics Simulations ◽  
Relative Motions

We study molecular arrangements and dynamics in alkyl ethoxylate nonionic surfactant micelles by combining high field (600 and 700 MHz) NMR relaxation measurements with large-scale atomistic molecular dynamics simulations. For spherical micelles, but not for cylindrical micelles, cross relaxation rates are positive only for surfactant alkyl tail atoms connected to the hydrophilic head group. All cross relaxation rates are negative for cylindrical micelles. This effect is reproducible either by changing composition (ratios of the nonionic surfactants) or changing temperature of a single surfactant in order to change the micelle shape. We validate the micelle shape by SANS and use the results as a guide for our simulations. We calculate parameters that determine relaxation rates directly from simulated trajectories, without introducing specific functional forms. Results indicate that relative motions of nearby atoms are liquid-like, in agreement with 13C T1 measurements, though constrained by micelle morphology. Relative motions of distant atoms have slower components because the relative changes in distances and angles are smaller when the moving atoms are further apart. The slow, long-range motions appear to be responsible for the predominantly negative cross relaxation rates observed in NOESY spectra. The densities of atoms from positions 1 and 2 in the boundary region are lower in spherical micelles compared to cylindrical micelles. Correspondingly, motions in this region are less constrained by micelle morphology in the spherical compared to the cylindrical cases. The two effects of morphology lead to the unusual occurrence of positive cross relaxation involving positions 1 and 2 for spheres.

Stereoisomerization during Molecular Packing

2021 ◽  
pp. 2100986
Author(s):  
Shidang Xu ◽  
Yukun Duan ◽  
Purnima Manghnani ◽  
Kenry ◽  
Chengjian Chen ◽  
...  
Keyword(s):  
Molecular Packing

Unveiling the crystalline packing of Y6 in thin films by thermal induced “backbone-on” orientation

2021 ◽  
Author(s):  
Yiqun Xiao ◽  
Jun Yuan ◽  
Guodong Zhou ◽  
Ka Chak Ngan ◽  
Xinxin Xia ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Organic Solar Cells ◽  
High Performance ◽  
Molecular Packing

Researchers are endeavoring to decode the fundamental reasons for the non-fullerene acceptor, Y6, to deliver high-performance organic solar cells. In this manuscript, we tackle this problem from the molecular packing...

scholarly journals Paclitaxel loading in cationic liposome vectors is enhanced by replacement of oleoyl with linoleoyl tails with distinct lipid shapes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuhong Zhen ◽  
Kai K. Ewert ◽  
William S. Fisher ◽  
Victoria M. Steffes ◽  
Youli Li ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Membrane Structure ◽  
Cationic Liposome ◽  
Solubility Limit ◽  
Loading Capacity ◽  
Prostate Cancer Cells ◽  
X Ray ◽  
X Ray Scattering ◽  
Cylindrical Micelles ◽  
Molecular Affinity

AbstractLipid carriers of hydrophobic paclitaxel (PTX) are used in clinical trials for cancer chemotherapy. Improving their loading capacity requires enhanced PTX solubilization. We compared the time-dependence of PTX membrane solubility as a function of PTX content in cationic liposomes (CLs) with lipid tails containing one (oleoyl; DOPC/DOTAP) or two (linoleoyl; DLinPC/newly synthesized DLinTAP) cis double bonds by using microscopy to generate kinetic phase diagrams. The DLin lipids displayed significantly increased PTX membrane solubility over DO lipids. Remarkably, 8 mol% PTX in DLinTAP/DLinPC CLs remained soluble for approximately as long as 3 mol% PTX (the solubility limit, which has been the focus of most previous studies and clinical trials) in DOTAP/DOPC CLs. The increase in solubility is likely caused by enhanced molecular affinity between lipid tails and PTX, rather than by the transition in membrane structure from bilayers to inverse cylindrical micelles observed with small-angle X-ray scattering. Importantly, the efficacy of PTX-loaded CLs against prostate cancer cells (their IC50 of PTX cytotoxicity) was unaffected by changing the lipid tails, and toxicity of the CL carrier was negligible. Moreover, efficacy was approximately doubled against melanoma cells for PTX-loaded DLinTAP/DLinPC over DOTAP/DOPC CLs. Our findings demonstrate the potential of chemical modifications of the lipid tails to increase the PTX membrane loading while maintaining (and in some cases even increasing) the efficacy of CLs. The increased PTX solubility will aid the development of liposomal PTX carriers that require significantly less lipid to deliver a given amount of PTX, reducing side effects and costs.

Energetics and Optimal Molecular Packing for Singlet Fission in BN-doped Perylenes: Electronic Adiabatic State Basis Screening

2021 ◽  
Author(s):  
Anurag Singh ◽  
Alexander Humeniuk ◽  
Merle Insa Silja Röhr
Keyword(s):  
Electronic Properties ◽  
Molecular Packing ◽  
Photovoltaic Devices ◽  
Singlet Fission ◽  
Adiabatic State

Singlet fission has the potential to increase the efficiency of photovoltaic devices, but the design of suitable chromophores is notoriously difficult. Both the electronic properties of the monomer and the...

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