Aviram

A Schejter, I Aviram, T Goldkorn. The contribution of electrostatic factors to the oxidation-reduction potentials of c-type cytochi omes. In C Ho, ed. Electron Transport and Oxygen Utilization. New York Elsevier North-Holland, 1982, pp 95-109. 

KAPLAN M and AVIRAM M (1999) Oxidized low density lipoprotein atherogenic and proinflammatoiy characteristics during macrophage foam cell formation. An inhibitory role for nutritional antioxidants and serum paraoxonase Clinical Chemistry Laboratory Medicine 37,111-9,1. 

FUHRMAN B, AViRAM M (2001) Flavonoids protect LDL from oxidation and attenuate atherosclerosis, Current Opinion in Lipidology, 12, 41-8. 

HAYEK T, FURHMAN B, VAYA J, ROSENBLAT M, BELINRY P, COLEMAN R, ELIS A, AVIRAM M (1997) Reduced progression of atherosclerosis in apolipoprotein E-deficient mice following consiunption of red wine, or its polyphenols quercetin or catechin, is associated with reduced susceptibility of LDL to oxidation aggregation, Arteriosclerosis, Thrombosis and Vascular Biology, 17, 2744-52. 

As other examples one may quote the symmetry-breaking of the CASSCF (4e in 4MO) calculation of the inn twisted excited state of ethylene (G. Trinquier and Malrieu, in "The structirre of Double Bond". Patai ed., John Wiley (1990) p 1, or the symmetry-breaking in electron transfer problems (A. Faradzed, M. Dupuis, E. dementi and A. Aviram, J. Amer. Chem. Soc. 112, 4206 (1992). 

Aviram, A., Seiden, P., Ratner, M. A., in Molecular Electronic Devices, Carter, F. L. (ed.), New York—Basel, Marcel Dekker 1983... 

Flavonoids protect LDL from oxidation, delaying the onset of lipid peroxidation, however, the prevention of atherosclerosis by flavonoids occurs not only by the inhibition of LDL oxidation, but also by the increase of cellular resistance to harmful effects of the oxidized LDL (de Luis and Aller, 2008). The antioxidant activity of anthocyanidins, as well as their protective role against LDL oxidation, has been well demonstrated in different in vitro systems (Aviram and Fuhrman, 2002 Satue-Gracia and others 1997 Teissedre and others 1996). 

Flavonoids are present in other beverages besides wine and tea. For example, pomegranate and cranberry juice contain high concentrations of polyphenols and a strong antioxidant activity against LDL oxidation. Their antioxidant capacity depends not only on the amount but also on the type of flavonoids present (Aviram and Fuhrman 2003). 

Aviram M and Fuhrman B. 2003. Effects of flavonoids on the oxidation of LDL and atherosclerosis. In Rice-Evans C and Packer L, editors. Flavonoids in Health and Disease, 2nd ed. Boca Raton, FL CRC Press, pp. 165-203. 

Aviram M, Fuhrman B. 2002. Wine flavonoids protect against LDL oxidation and atherosclerosis. Ann N Y Acad Sci 957 146-161. 

Rozenberg O, Howell A and Aviram M. 2006. Pomegranate juice sugar fraction reduces macrophage oxidative state, whereas white grape juice sugar fraction increases it. Atherosclerosis 188(1 ) 68-76. 

Aviram A, Ratner MA (1974) Molecular rectifiers. Chem Phys Lett 29(2) 277-283... 

Joachim C, Gimzewski JK, Aviram A (2000) Electronics using hybrid-molecular and mono-molecular devices. Nature 408(6812) 541-548... 

UE began with Aviram and Ratner s 1973 proposal for a molecular rectifier this is the third rectification process [79]. An Aviram-Ratner rectifier has donor and acceptor groups in one molecule, separated by an insulating bridge of sigma... 

Fig. 10 Aviram-Ratner rectification via HOMO and LUMO. (a) A D-o-A molecule is sandwiched between two metal electrodes. MD is the electrode proximal to the donor, MA is the electrode proximal to the acceptor, is the electrode metal work function, IPD is the ionization potential of the donor, EAa is the electron affinity of the acceptor, (b) No pathway for current exists when a voltage is applied in the reverse bias direction, (c) Under a comparable voltage to (b) but in the forward bias direction, rectification results from electrons flowing from MA to LUMO to HOMO to MD...

The Aviram-Ratner D-ct-A molecule is analogous to a pn junction rectifier the electron-rich donor region D would be similar to the electron-rich semiconducting n region, while the electron-poor A region would be similar to a semiconductor s p region [79]. However, note that under forward bias the preferred direction of Aviram-Ratner electron flow is from A to D, while in a pn junction rectifier the preferred direction is from n to p. 

Fig. II Aviram-Ratner rectification with centered donor and acceptor groups...

Under +1 V of forward bias (Fig. lid), there is no pathway for current flow. At +2 V, however, the orbitals have adjusted to give a downhill path from MA to acceptor to donor to MD, and Aviram-Ratner current flows. On the reverse bias side, however, two pathways exist for current flow at —1 V (Fig. 1 lb) as well as —2 V (Fig. 11a). These pathways (Fig. 11a, b) are asymmetric rectification via HOMO and via LUMO, and they are in the anti-Aviram-Ratner direction, i.e., from donor to acceptor. This could allow for anti-Aviram-Ratner rectification under moderate biases. Note, however, that the electrons in Fig. 11a, b must tunnel over longer distances than those in Fig. lie, because there is only one way-station, instead of two. The Aviram-Ratner current flow under the higher bias of Fig. lie could therefore be much more intense than the reverse flow of Fig. 1 lb or 1 la. 

Aviram and Ratner s originally proposed D-a-A molecule (or Gedankenmolekiil ), 35 (Fig. 14), included the excellent donor TTF (27) and the excellent acceptor TCNQ (33), separated by a rigid bicyclooctane bridge [79]. This molecule was never made (and would likely not have made a good monolayer), but it was the impetus for the synthesis of many new candidate rectifiers. 

Fig. 14 Aviram-Ratner proposed D-o-A molecule for unimolecular rectification...

Among the early potential rectifiers studied, one of us (Mattem) designed the D-cr-A molecule 37 (Fig. 17), whose multilayer conductivity was measured by the Sambles group [99]. Multilayers gave striking rectification, with RR = 130. Current flow was in the anti-Aviram-Ratner direction, however, and having an assembly of multilayers rather than a monolayer complicated the interpretation of the results [99]. 

Characteristic IV curves at room temperature are shown in Fig. 18, and some of the results are summarized in Table 1. These results have been reviewed often [11, 12]. Efforts were made to identify the molecular mechanisms for the rectification, and to buttress them by theoretical calculations [39, 76, 106, 112]. Not all compounds tested rectified, because of their chemical structure and/or monolayer structure. The direction of larger electron flow ( forward direction ) is shown by arrows in Fig. 16 it is noteworthy that in all cases the direction is from the electron donor D to the electron acceptor A, that is, in the anti-Aviram-Ratner direction. 

For most of the molecules, the electron flow is from D to A, which is supported by the anti-Aviram-Ratner mechanism of Fig. 11a. However, there may be yet another possibility, shown in Fig. 21 implicit in the analyses of Figs. 9-11 has been the Aviram and Ratner assumption [79] that auto-ionization is a less efficient competing process. If the electric field induces intramolecular ionization first by sufficiently altering the orbital energies, then the direction of electron flow may occur in the anti-AR direction (Fig. 21) ... 

---