Structural Analysis
Nuclear Magnetic Resonance (NMR) is one of the most important spectroscopic methods currently used to describe the structure and dynamics of a variety of molecular and macromolecular systems. The importance of this method is clearly illustrated by the fact that six Nobel Prizes have been awarded for the development of NMR (O. Stern (1943), I.I. Rabi (1944), F. Bloch and E.M. Purcell (1952), R.R. Ernst (1991), K. Wüthrich (2002), P.C. Lauterbur and P. Mansfield (2003)). Today one can find important applications of NMR spectroscopy in structural biology describing the structure and function of nucleic acids or proteins, or in industry identifying new drugs or the products of their metabolism. NMR spectroscopy is thus an indispensable part of the current protemic and metabonomic research. In addition, recent methodology and hardware developments significantly increase the resolution and selectivity of solid-state NMR experiments that now provide detailed information on the structure and dynamics of a wide range of organic and inorganic solids. In many cases, solid-state NMR spectroscopy became quite comparable with well-established x-ray diffraction techniques, thus opening new ways to characterize nanocrystalline and microcrystalline powdered solids. The time has come for NMR crystallography.
Development and application of NMR crystallography for active pharmaceutical ingredients and materials thus currently represents one of our main research directions. Quite related is our research of the volume phase transitions of synthetic thremoresponsive polymers for biomedical applications, and/or the investigation of complex interactions and behavior of natural biopolymers and polysaccharides such as alginate gels and microbeads designed for cell transplantations. An important application of NMR spectroscopy also lies in the development of advanced catalysts based on aluminosilicate and metal-organic frameworks. Such a research is a base of our work in the Joint laboratory of solid-state NMR spectroscopy which we run together with the Jaroslav Heyrovsky Institute of Physical Chemistry CAS, our partner. In this laboratory we extensively investigate structure and dynamic processes in nanocpomposites and advanced electric and ion-conductive materials for energy applications. Research of our department thus nearly completely cover trends in current material science and allows us to fill the needs of other centers of the Institute of Macromolecular Chemistry CAS. In addition, this research directly follows the recently formulated strategy of the Czech Academy of Sciences called as Strategy AV21, which is based on the cross-disciplinarily and inter-institutional cooperation.
The Center STRUCTURE, Department of NMR Spectroscopy and the integrated Joint laboratory of solid-state NMR spectroscopy thus represent a core of the Research Programme “VP10-Molecules and Materials for life” of the Strategy AV21. This Research Programme, “VP10-Molecules and materials for life”, is coordinated in the Center STRUCTURE by dr. Jiri Brus and gathers four institutes of the Czech Academy of Sciences. All news, activities and results of the programme VP10, are summarized and updated in the two websites of the programme: MOL&MAT and MOL&MAT-news.
The department of NMR spectroscopy has been at the end of 2020 extended by incorporating the research group of X-ray and neutron diffraction. In July 2023, the department was further extended by incorporating the Vibrational spectroscopy research group.
X-ray powder diffraction (XRD) is a non-destructive analytical technique used for phase identification of crystalline or polycrystalline materials. It can provide information on the crystal structure, atomic spacing and dimensions of the ground cells. In the case of polymeric materials, it is commonly used to determine the degree of crystallinity and the representation of each phase. Small-angle X-ray scattering (SAXS) is a widely used technique for investigating 3D structures over a wide size range from approximately 1 nm to 100 nm. With the recent development of advanced X-ray sources and detectors, this technique has become a major tool for the comprehensive characterization of macromolecules and nanostructured materials. From the evaluation of the scattering profile, information on particle shape, size or size distribution can be obtained. In this list, one cannot omit GISAXS (Grazing-Incidence Small Angle X-ray Scattering), a unique and very advanced research method dealing with the detection and characterization of laterally organized structures in thin films.
The vibrational spectroscopy methods allow obtaining detailed information on the composition of blends, molecular structure, conformations and intra- and intermolecular interactions of molecules. Infrared spectroscopy (IR) sensitively detects polar groups in the structure of the molecule which makes it an ideal method of analysis of completely unknown samples and systems with interactions on polar groups i.e. hydrogen bonds. Raman spectroscopy is more sensitive to non-polar and symmetrical structures, so it reflects the carbon backbone of the molecule better. Raman scattering is a weak effect on its own, but it can be enhanced, enabling selective detection of specific species: Resonance Raman spectroscopy (RRS) is based on a resonance of the exciting radiation with electronic transitions in a molecule and enhances the Raman signal of chromophores; Surface enhanced Raman spectroscopy (SERS) is sensitive to molecules in a close vicinity of metal nanoparticles. We can combine all mentioned methods with microscopy to gain structural information with spatial resolution (Microspectroscopy). Vibrational spectroscopy methods can be combined with an electrochemical experiment allowing the study of electrochemical processes in-situ (Spectroelectrochemistry).
NMR crystallography of active pharamceutical ingredients and material
Besides the sophisticated synthesis development of a next generation of advanced pharmaceuticals requires detailed insight into their molecular and crystal structure. Nuclear Magnetic Resonance (NMR) with its potential to probe structure of solids at atomic-resolution level thus seems to be nearly a universal method. Namely in the Joint Laboratory of Solid-State NMR Spectroscopy in tight cooperation with universities and pharmaceutical companies we are developing advanced techniques of solid-state NMR crystallography which allows efficient and reliable monitoring of manufacture of pharmaceutical products, easy identification of polymorphic impurities as well as precise description of crystal structures of complex active pharmaceutical ingredients.
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Peptide derivatives of boronic acid and their unique structure. Boron-containing compounds have long been recognized as potentially active pharmaceutical ingredients. As recent investigations have resulted in the discovery of many promising pharmaceuticals exhibiting anticancer and antibacterial activity, the research of peptidic derivatives with boronic acid fragment is rapidly gaining in intensity. Uncertainties in the structure determination of these peptide analogues, however, represent an obstacle in understanding their role in living organisms and thus also in developing next generation of anticancer drugs. For full exploitation of these systems we develop efficient a generalized experimental-computational strategy allowing atomic-resolution structure determination of the complex boronic acid derivatives even in the absence of single crystals which is quite a typical situation for a wide range of pharmaceutical solids.
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Hybrid materials and nanomaterials for biomedical applications. In the field of biomedicine, recent effort in optimizing therapeutic efficacy of newly discovered compounds has resulted in the development of a range original supramolecular systems. In this regard silica microparticles, virus-like vectors, liposomes, metalorganic frameworks and a range of polymers have been successfully applied. Full exploitation of these systems however, still requires their precise physicochemical characterization. Unfortunately there are many obstacles that limit application of traditional analytical tools. Primarily this is the multicomponent nature of the drug-delivery systems, their semicrystalline character, low concentration of the active compounds, unpredictable polymorphism and extensive structural diversity. In collaborations with pharmaceutical companies we systematically develop computational-experimental approaches, which provide clear insight into these complex multicomponent systems in which active compounds often exist in exotic physical states and forms such as organogels.
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Structure of polysaccharides and their interactions
Following extensive development of advanced biomaterials we also deal with the structure and dynamics of natural polysaccharides such as cellulose, starch, alginates, chitosan and glucans.
Alginates (ALGs), naturally occurring biopolymers obtained from brown sea algae, currently are finding an increasing number of applications in many areas of human life. They are widely used in the delivery of many bioactive agents, in tissue engineering for cell transplantation, in regenerative medicine, and in other modern medical techniques, including the assembly of advanced medical devices. The applications of ALGs are, however, much wider and go beyond the field of biomedicine. The application of ALG gels as materials for capturing toxic metal ions such as Pb2+ and Cd2+ from waste water is very promising. Surprisingly, however, almost nothing is known about their structural transformations in physiological environments. The absence of structural data describing the structural changes in ALG gels at different pH values mimicking body fluids is particularly surprising considering the recently described successful biomedical applications of ALG gels crosslinked by potentially toxic ions such as Al3+, Ba2+ or Sr2+.
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On the molecular level, ALG polymers consist of α-L-guluronic acid (G) and β-D-mannuronic acid (M) residues. These residues are linked by 1-4 glycosidic bonds, forming homopolymeric blocks of G units (GG blocks) or M units (MM blocks) and heteropolymeric sequences of randomly coupled G and M units (GM blocks). When the polymer chains are crosslinked by polyvalent ions, typically by Ca2+ ions, alginate gels are formed.
Advanced polymer composites and ion-conductive materials
Clean energy, global warming, reducing emissions - terms currently often introduced in a variety of meanings and contexts. Effective utilization of solar and wind energy, and spreading the use of electric vehicles and portable electronic raises the demand for electric-energy-conversion and storage devices. Our effort is thus focused on the synthesis, optimization and detailed strucutral characterization of innovative inorganic and hybrid functional materials exhibiting electric and ionic conductivity.
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Our cooperation with Prof. Feng Gao (Division of Biomolecular and Organic Electronics, Linköping University) has recently resulted in the development of perovskite-molecule composite thin films for efficient and stable light-emitting diodes. Although perovskite light-emitting diodes (PeLEDs) experienced significant progress, there were only scattered reports of PeLEDs with both high efficiency and long operational stability, which called for additional strategies to address this challenge.
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Polymers as well as Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) due to their inherent structural variability and well-defined porous architecture are thus predetermined to be explored as the materials suitable for developing Li-battery (LiBs) electrodes, all-solid-state electrolytes and fuel cell ion-conducting membranes. Consequently, structural studies of these systems are indispensable part of our current research.
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Advanced catalysts, inorganic framework materials and ultra-wide-line NMR spectroscopy
Chemical production is a key industrial activity of current civilization. The vast majority of industrial chemical manufacturing utilizes a variety of catalytic processes. Therefore, in order to achieve the most environmentally friendly chemical production, it is necessary to develop the most selective, least energy efficient processes.
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Zeolites are complex aluminosilicates, crystalline framework materials composed mainly by SiO4 corner-sharing tetrahedra. Therefore in collaboration with the Jaroslav Heyrovsky Institute of Physical Chemistry and as a part of the research project VP10 we focus on structural studies of zeolites and related framework materials.
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Structure and phase transitions of phermoresponsive polymer for biomedical applications
Structure, interactions and dynamical processes occurring during extensive phase-volume transitions of synthetic polymers in water solutions belong to the most typical subjects of our research for a long time. Currently we focus our attention on multiresponsive polymers which exhibit structural and functional changes upon modified pH, temperature, ionic strength or electromagnetic field and/or radiation.
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X-ray and neutron structural analysis of macromolecular systems
Our state-of-the-art facilities and technologies (GISAXS, XRR, XRPD, SAXS/WAXS) are mainly focused on the structural research of new polymers and polymer composites using X-ray scattering at small and large angles. Using X-ray diffraction and scattering in our laboratories, we are able to analyze materials non-destructively to determine their internal structure.
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Vibrational spectroscopy
The research areas of the Vibrational Spectroscopy group currently include self-organised systems based on block polymers, conducting polymers and related materials, electrolytes for lithium batteries, coatings and polymer blends.
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