scholarly journals Molecular modeling of DDT's and it's major metabolites adsorption in the interlaminar space of montmorillonite

2014 ◽  
Vol 1 (1) ◽  
pp. 12-19
Author(s):  
János Ecker ◽  
László Fülöp

A simple adsorption mechanism of the organochloride insecticide DDT and it's most common metabolites DDD and DDE in the interlaminar layer of montmorillonite mineral is discussed in this paper, based on the results of molecular modeling. A model of a simple fragment of the montmorillonite crystal with the interlaminar layer was created and used. The interlaminar layer contained water as a solvent and the ionic forms of sodium or calcium as exchangeable cations along with the molecules of DDT/DDD/DDE. The molecular interactions were simulated by force fields and the results of the simulation could be explained by the physical characteristics of the models which were studied with bioinformatics tools as well. Based on the observed mechanisms, the adsorption of DDT and it's metabolites in the interlaminar layer of montmorillonite is possible and it is partly responsible for the persistent nature of these insecticides.

2021 ◽  
Vol 5 (4) ◽  
pp. 147
Author(s):  
Petr A. Ryapolov ◽  
Eugene B. Postnikov

In this work, we show that the static magnetization curve of high-concentrated ferrofluids can be accurately approximated by the Mittag–Leffler function of the inverse external magnetic field. The dependence of the Mittag–Leffler function’s fractional index on physical characteristics of samples is analysed and its growth with the growing degree of system’s dilution is revealed. These results provide a certain background for revealing mechanisms of hindered fluctuations in concentrated solutions of strongly interacting of the magnetic nanoparticles as well as a simple tool for an explicit specification of macroscopic force fields in ferrofluid-based technical systems.


Author(s):  
Xiaoyong Cao ◽  
Pu Tian

Molecular modeling is widely utilized in subjects including but not limited to physics, chemistry, biology, materials science and engineering. Impressive progress has been made in development of theories, algorithms and software packages. To divide and conquer, and to cache intermediate results have been long standing principles in development of algorithms. Not surprisingly, Most of important methodological advancements in more than half century of molecule modeling are various implementations of these two fundamental principles. In the mainstream classical computational molecular science based on force fields parameterization by coarse graining, tremendous efforts have been invested on two lines of algorithm development. The first is coarse graining, which is to represent multiple basic particles in higher resolution modeling as a single larger and softer particle in lower resolution counterpart, with resulting force fields of partial transferability at the expense of some information loss. The second is enhanced sampling, which realizes "dividing and conquering" and/or "caching" in configurational space with focus either on reaction coordinates and collective variables as in metadynamics and related algorithms, or on the transition matrix and state discretization as in Markov state models. For this line of algorithms, spatial resolution is maintained but no transferability is available. Deep learning has been utilized to realize more efficient and accurate ways of "dividing and conquering" and "caching" along these two lines of algorithmic research. We proposed and demonstrated the local free energy landscape approach, a new framework for classical computational molecular science and a third class of algorithm that facilitates molecular modeling through partially transferable in resolution "caching" of distributions for local clusters of molecular degrees of freedom. Differences, connections and potential interactions among these three algorithmic directions are discussed, with the hope to stimulate development of more elegant, efficient and reliable formulations and algorithms for "dividing and conquering" and "caching" in complex molecular systems.


2009 ◽  
Author(s):  
R. Chaudret ◽  
S. Ulmer ◽  
M.-C. van Severen ◽  
N. Gresh ◽  
O. Parisel ◽  
...  

2018 ◽  
Vol 3 (4) ◽  
pp. 619-626 ◽  
Author(s):  
Mansi S. Shah ◽  
Evgenii O. Fetisov ◽  
Michael Tsapatsis ◽  
J. Ilja Siepmann

Selective zeolitic frameworks for adsorptive separation of ethane and ethylene are identified using molecular modeling with improved force fields.


2004 ◽  
Vol 844 ◽  
Author(s):  
Rahul Bhowmik ◽  
Kalpana S Katti ◽  
Dinesh R Katti

AbstractNanocomposites of polymer and hydroxyapatite are widely used as bone replacement materials. The mechanical responses of these nanocomposites are known to be influenced by molecular interactions at mineral polymer interface. Molecular modeling of these interactions is an area of current interest but force field parameters of such dissimilar molecules are not available for a common force field. Also, parameters for several commonly used force fields are not available in the literature for hydroxyapatite. Recently a unique force field was described in literature that represents the structure of hydroxyapatite reasonably well. Yet the applicability of this force field for studying the interaction between dissimilar materials (such as mineral and polymer) is limited as there is no accurate representation of polymer. CVFF is a commonly used force field for which parameters of many material systems are available. We have obtained the parameters of CVFF for monoclinic hydroxyapatite from the known potential energy function of apatites and from experimentally obtained infrared spectra. Validation of simulations is done by comparison of computationally obtained unit cell parameters, vibrational spectra and different atomic distances with experiments. This study represents molecular modeling of polymermineral interfaces with the known parameters of hydroxyapatite.


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