Prof. Amir Berman
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Senior lecturer
Department :
Department of Biotechnology Engineering
Room :
Phone :
972-74-7795264
972-74-7795263
972-74-7795262
Email :
aberman@bgu.ac.il
Office Hours :
Education
B.Sc. -1981-1983: The Hebrew University of Jerusalem. Faculty of Agriculture (Rehovot), Department of Soil Science. (Cum Laude).M.Sc. -1985-1987: Weizmann Institute of Science. Dept. of Isotope research. Advisors: Profs. Lia Addadi and Steve Weiner. Title of thesis: Intracrystalline Acidic Glycoproteins from Sea Urchin Tests and Mollusk Shells. Ph.D. - 1987-1992: Weizmann Institute of Science, Department of Structural Biology. Advisors: Profs. Lia Addadi and Steve Weiner. Title of Thesis: Intracrystalline Proteins: Control of Single Crystal Texture and Properties in Biomineralization
Research Projects
An underlying theme in my research of biomimetic materials borrows from the natural systems. In this approach, natural interafcial processes are identified, reconstructed and studied in vitro. The studies on template directed ctystal nucleation is one such system that imitate some aspects of natural biomineralization system, and use it as a source of inspitration. The elucidated principles are used for the deposition of ordered arrays of nanocrystalline semiconductor particles. The same line of research is employed in a totally different context. Lung-surfactants are presently being studied (project #7) in-vitro, in a monolayer set-up in which different environmental and clinical situations are imitated and simplified and their physico-chemical and clinical ramifications are analyzed. The molecules of choice for producing some of the monolayer films I study are polydiacetylenes (PDA). Long chain amphiphiles, with diacetylene functionality are used to form compressed Langmuir monolayers at the air-water interface. The monolayer films are then UV-polymerized. These polymerized films posses several salient features that render them suitable for my research goals. The polymer is linear, unbranched, and geometrically straight molecule with conjugated (yne-ene) backbone. Due to the PDA very long conjugation length, it absorbs visible light. Its linear conformation makes this molecule a possible electron (photo-) conductor in one dimension. PDA assemblies are sensitive to mechanical deformations that shorten the conjugation length and as a consequence, blue-shift the visible absorption spectra. The change in the electronic structure is also associated with change in the electrical conductance properties of the polymer (project #5). The sensitivity of the PDA to external changes in its environment, and its visual and electrical response, make it an ideal candidate as a basis for chemical and biological sensors. The moieties on the PDA interface can be derivatized at will, thus giving it different recognition surface properties. The crystalline, closely packed surface groups, render the film very sensitive to various sterical constraints that take place at its interface. Specific chemical or biological recognition will thus be expressed by deformation of the film, causing the expected change in color and electrical properties (projects #2, #6 & #9). A central challenge in my research is to design a system in which the PDA planar array undergoes deformation in a predictable and ordered manner. A system that offers such prospect is based on the formation DNA base-pairs between DNA single strand and complementary derivatized PDA film (project #2). There, the regular period along the strands is closely matched by the period of the PDA headgroups along the polymer backbone. Nucleobases on the polymer and in the complementary single-stranded DNA have the same planar cross-section and similar periodicty, hence steric hindrance is not expected to be significant. Rather, the formed PDA-DNA hybrid base-pairs are expected to stack and induce coiling of the supramolecular hybrid, due to packing considerations similar to native DNA helix formation. It is expected that the structured deformation that take place along the common direction of the PDA and DNA will have distinct effect on the film color and electrical conductance. This has many consequences: for the field of colorimetric biosensors it is one of the few ‘non-random’ conformational responses. A possible outcome of this study can therefore be the improvement of the efficacy of colorimetric biosensors response. Moreover, since the electronic ?-system is altered, change in the electrical conductance is anticipated. This offers a novel mode of modulation of conductance in conjugated polymers that is based on reversible chemical recognition. Combined with the evident molecular directionality of the PDA domains it can be used in future ‘molecular devices’ (project #5). Monolayers of PDA have been shown to be efficient templates for crystal nucleation (project #1). It has been shown that epitaxial relationship take place at the organic-inorganic interface, regardless of their very different chemical and structural nature. Directed inorganic crystal nucleation on organic templates is very common in Nature, known as biomineralization. The PDA as a model template has many advantages. It is fairly rigid film due to polymer conjugated bonds system; has very large domains. The PDA film is anisotropic, therefore birefringence in polarized light, hence it is possible to relate macroscopic features directly to its molecular orientation. These virtues allow various spectroscopic and scanning probe techniques to be employed in the study of surface interactions and their directionality. We take advantage of these PDA properties in the study of directed crystal nucleation of calcite as well as other different semiconductive nanocrystals in a biomimetic methodology. In an on going research, we produce CdS nano particles on PDA films. The particles reveal uniform cluster orientation with respect to the polymer substrate and are aligned with one crystallographic axis coinciding with it. Elucidating the structural requirements for surface crystal nucleation can yield better understanding of initial stages in biomineralization processes and find uses in various technological applications. The structural relationship across this organic-inorganic interface is the central question in this study, which is currently addressed experimentally with grazing angle x-ray diffraction using synchrotron radiation. These experiments are carried out at the European Synchrotron Radiation Facility (ESRF) at Grenoble, France. So far four experimental session have been carried out there, and yielded in-depth understanding of the structural details that accompany the important 'blue' to 'red' transition in PDA. Molecular order at surfaces, and processes of self aggregation and organization of molecules can give rise to (lateral) pattern formation at the nanometre scale. Todate, such patterns can be spontaneously formed, but control of their precise shape is beyond reach. Developing capabilities to induce order from the molecular-level, up to the sub-micrometer level is a major challenge and a bottleneck for the incorporation organic molecules and polymers into the realm of thin film molecular electronics. The potential ability to induce such surface patterns will undoubtedly open doors to many novel applications. These may include miniature devices integrating chemical and biological assays with optical and microelectronics circuitry. Research program aimed at forming a one monolayer-thick patterns of lipids at the air-solution interface with surface waves is under way (project #4). An integrative project, aiming at combining several aformentioned functionalities in single PDA domain, is underway (projects #1,2,5,6). Briefly, the vision is to produce PDA mixed domains that have areas that can nucleate crystals (i.e. light-sensitive semiconductor particles) and nearby areas with molecular recognition capabilities, on the same polymer backbone. This assembly is expected to function as a self contained chemical sensor, having recognition, signal transduction, and reporting (by change of color or electrical impedance) capacities. This has recently gave rise to a funded project for the develpoment of a remote chemical sensors that is based on the structural, electro-optical and spectral transitions of PDA (#9). In a new research project (#8) with A. Sagi (Dept. of Life Science) we study yet another aspect of the complex organic and inorganic interfaces in materials. Together we study, each from his own perspective, the physiological and biominerological pathways by which certain decapods inhibit the crystallization of their hard parts, despite their thermodynamic tendency to crystallize. The formed mineral - amorphous calcium carbonate, ACC, is highly soluble yet rigid and protective. This facinating mechanism is a unique biological adaptation to limited environmental calcium availability conditions, and the need to the rapid mobilization of the mineral during the molting stage. It represent one of the few cases known todate in Nature, where organisms exert such control over their mineralization process, and present an important challenge to materials scientists, regarding possible novel ways to artificially control the degree of crystallinity of materials. Research projects in progress 1. Oriented nucleation of CdS, PbS and other metal sulfides nanoparticles on polymerized monolayers. (with Y. Golan) 2. Recognition of single-stranded DNA by a complementary derivatized films. 3. Controlled nucleation and growth of calcite crystals. A biomimetic approach. 4. Micrometer size surface waves as a mean to induce patterns and order in monolayers at the air-solution interface. (with L. Likhterov and R. Granek). 5. Anisotropic electronic properties of polydiacetylene films. (with B. Horovitz and Y. Golan) 6. Colorimetric biosensor study on PDA-phospholipid mixed membrane model (with R. Jelinek) 7. Studies on Lung surfactant poisoning and operation (with R. Granek and E. Zmora (Soroka H.) 8. Biomineralization mechanism of amorphous calcium carbonate deposition in fresh water crayfish (Crustacea), a combined mineralogy and biochemical approach. (with A. Sagi) 9. Development of a remote chemical sensor for hazardous and explosive material vapour based on the induced phase transiti