CMAST (Computational MAterials Science & Technology) Virtual Labwww.afs.enea.it/project/cmast

Computational Materials Science

MATERIALS FOR NANOTECHNOLOGIES

Functionalization of virus-like nanoparticle

Project:• Progetto Grande Rilevanza, Ministero affari Esterni, bilaterale

Italia-Giappone “Sfide globali per la salute. Biofarmaci derivati da pianta”C. Arcangeli(ENEA)

Problem: The discovery of new generation nanoparticles is one of the most active areas of nanotechnoloy. Virus-like particles (VLPs) are nature-made nanometer-sized objects and are formed by coat protein (CP) self-assembly. Such nanoparticles can be functionalized by gene engineering or chemical modifications of the CP subunits and exploited to produce safe vaccine vehicles and nanoparticles for drug delivery. However, if not carefully designed, the functionalization could have negative effects on the VLPs self-assembly and stability. In silico method can represent a valid tool for the rational design of functionalizated VLPs. Open questions:1) What are the effects of the insertion of immunogenic epitopes on the

packing of the subunits and on the stability of chimeric VLPs?

Method:Homology Modeling (HM) and Molecular Dynamics (MD) simulations are used to model the VLPs. The simulated system is composed by ca. 4 millions of atoms.

Results:• the structural analysis of the VLP models detected interdomain interactions important for the stability• the in silico protocol represents an effective screening tool to design the fusion of different epitopes on the VLP. The method is able to predict both positive and negative results as requested by the fail-fast fail-cheap phyiosophy embraced by the pharmaceutical companies.

VLP-V3pos1 VLP-V3pos3

VLP-V3Cter

failed rmsd ~ 1nm

rmsd < 1nm

VLP-2F5Cter

rmsd < 0.8 nm

Theoretical predictions of the suitable positions on the CP where to insert the of immunogenic epitopes (i.e. HIV-1 V3 loop and HIV-1 2F5).

Structural properties (RMSD, Rg and number of clusters) of the VLP (solid line) and single CP (dashed line) as a function of simulation time.

C.- Arcangeli (ENEA)

Polymeric electronic materials and devices

Projects:• FIRB Italnanonet (MIUR) in collaboration with

STMicroelectronics• TECOP (sviluppo di nuovi materiali per automotive ed

aeronautica). Ministero dello Sviluppo Economico.

G. Milano, Dipartimento di Chimica e Biologia, Università di Salerno

Results:• Atomic structures of NP/Polymer Interfaces can be generated• The molecular picture resulting from simulations can confirm some of the hypothesis made on the

basis of macroscopic behavior. In particular, the effect of coating layer and the molecular orientation of the 8-HQ molecules with respect to nanoparticle surfaces

Problem: The new class of organic devices for microelectronics need a deep understanding of the interaction of nanoparticles in polimeric matrices. For this reason the effect of grafting on Gold NP/Polymer Interfaces is needed.

Open questions:1) Which is the the structure of Gold NP/Polymer Interfaces at atomic resolution2) How are affected the macroscopic properties by the Interface Structure

Method:Multiscale modeling based on Coarse-grained models and atomistic structures coming from reverse mapping procedure. Both models are simulated using Molecular Dynamics simulations

Al electrode

Polystyrene

Donor Acceptor: 8HQ and Gold Nanoparticle

Coarse-

Graining

Reverse -

Mapping

ATOMS

SUPERATOMS

CdS quantum dotsE. Burresi, ENEA Faenza

Problem: The stability of the CdS phase, and particularly the stability of phase between bulk and nanostructure material, continues to be now discussed but not entirely understood . It is necessary to investigate structural modifications in order to evaluate as electronic and optical properties are subject to change.

Open questions:1) Which is the the atomic structure of the CdS surface ?2) How the modification on the surface affect the electronic properties ?

Method:

Ab inito molecular dynamics was performed on cluster build up with 48 cadmium atoms and 48 sulfur atoms. This structure was heated from 100K to 600K . Structural and electronic properties of the cluster were accurately investigated for each temperature.

Snapshot of CdS wurtzite cluster. In yellow sulphur atoms and blue cadmium atoms. Sticks are used to enlight the first shell of coordination of each atom.

Results: From Ab-initio calculation on small single wurtzite CdS nanoparticle quantum dots, a substantial modifications of surface is find out after 300 K which reduce the surface effects.; in addition this structural change cause some alterations of the intermediate electronic states around the band gap, and the atoms on the surface have a main role on the formation of the intermediate states on the band gap.

Density of states for CdS cluster at T= 100 K (CdS100), T= 280 K (CdS280), T= 330 K (CdS330)

The lowest unoccupied molecular orbital for CdS cluster heated at 100 K

CdS cluster heated at 340 K: the lowest unoccupied molecular orbital is reported.

Organic nonvolatile memory devices made from a polystyrene (PS) film containing gold nanoparticles and 8-hydroxyquinoline (8-HQ) sandwiched between two metal electrodesshows a programmable electrical bistability.

Snapshot of sthe ystem howing some polymer chains closer to the nanoparticle surface. Polymer chains approach the nanoparticle surface exposing mainly the phenyl rings (white color). The backbone carbons are in blue, hydrogen atoms are omitted for clarity.

Snapshot of the system showing some polymer chains closer to the nanoparticle surface. Similarly, to the other system polymer chains approach the nanoparticle surface exposing mainly the phenyl rings (white color) some of the phenyl rings penetrate trough the alkyl chains layer (in red). The backbone carbons are in blue, the thiols chains are depicted in red, hydrogen atoms are omitted for clarity.