Piotr Paluch - Academia.edu (original) (raw)

Papers by Piotr Paluch

Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, 2020

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an... more This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z′ = 1 polymorph (form II), crystallize in P21/c and P 1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z′ = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for...

Acta Crystallographica Section A Foundations and Advances, 2019

Magnetic Resonance in Chemistry, 2019

We show that a multi-selective excitation with Hadamard encoding is a powerful tool for 2D acquis... more We show that a multi-selective excitation with Hadamard encoding is a powerful tool for 2D acquisition of 13 C-13 C homo-nuclear correlations. This method is not designed to improve the sensitivity, but rather to reduce the experiment time, provided there is sufficient sensitivity. Therefore, it allows fast acquisition of such 2D spectra in labeled molecules. The technique has been demonstrated using a U-13 C-15 N histidine hydrochloride monohydrate sample allowing each point of the build-up curves of the 13 C-13 C cross-peaks to be recorded within 4 min 35 s, which is very difficult with conventional methods. Using the U-13 C-15 N f-MLF sample we have demonstrated that the method can be applied to molecules with fourteen 13 C resonances with a minimum frequency separation of 240 Hz.

Crystal Growth & Design, 2018

Apremilast (APR), an anti-psoriatic agent, easily forms isostructural cocrystals and solvates wit... more Apremilast (APR), an anti-psoriatic agent, easily forms isostructural cocrystals and solvates with aromatic entities, often disobeying at the same time Kitaigorodsky's rule as to the saturation of possible hydrogen-bonding sites. In this paper the reasons for this peculiar behavior are investigated, employing a joint experimental and theoretical approach. This includes the design of cocrystals with coformers having a high propensity towards the formation of both aromatic-aromatic and hydrogen-bonding interactions, determination of their structure, using solid-state NMR spectroscopy and X-ray crystallography, as well as calculations of stabilization energies of formation of the obtained cocrystals, followed by crystal structure prediction calculations and solubility measurements. The findings indicate that the stabilization energies of cocrystal formation are positive in all cases, which results from strain in the APR conformation in these crystal forms. On the other hand, solubility measurements show that the Gibbs free energy of formation of the apremilast:picolinamide cocrystal is negative, suggesting that the formation of the studied cocrystals is entropy driven. This entropic stabilization is associated with the disorder observed in almost all known cocrystals and solvates of APR.

The Journal of Organic Chemistry, 2018

With the use of inexpensive commercially available abietic acid, a whole series of abietane enone... more With the use of inexpensive commercially available abietic acid, a whole series of abietane enones have been prepared in high yields. The structures of all the products obtained were determined by comprehensive spectroscopic analysis with particular emphasis on the use of advanced NMR techniques, comparison with previously reported data, and where possible by single crystal X-ray diffraction. However, in cases where X-ray crystallography was not applicable or compounds tested were unstable, a final stereochemical assignment could be only inferred by electronic circular dichroism (ECD) supported by vibrational circular dichroism (VCD) to increase credibility. To reveal the relationship between structure and chiroptical properties we used combined experimental and theoretical analysis of geometries,

Journal of Magnetic Resonance, 2019

It has previously been shown that 14 N NMR spectra can be reliably obtained through indirect dete... more It has previously been shown that 14 N NMR spectra can be reliably obtained through indirect detection via HMQC experiments. This method exploits the transfer of coherence between single-(SQ) or double-quantum (DQ) 14 N coherences, and SQ coherences of a suitable spin-1/2 'spy' nucleus, e.g., 1 H. It must be noted that SQ-SQ methods require a carefully optimized setup to minimize the broadening related to the first-order quadrupole interaction (i.e., an extremely well-adjusted magic angle and a highly stable spinning speed), whereas DQ-SQ ones do not. In this work, the efficiencies of four 14 N excitation schemes (DANTE, XiX, Hard Pulse (HP), and Selective Long Pulse (SLP)) are compared using J-HMQC based numerical simulations and either SQ-SQ or DQ-SQ 1 H-{ 14 N} D-HMQC experiments on Lhistidine HCl and N-acetyl-L-valine at 18.8 T and 62.5 kHz MAS. The results demonstrate that both DANTE and SLP provide a more efficient 14 N excitation profile than XiX and HP. Furthermore, it is shown that the SLP scheme: (i) is efficient over a large range of quadrupole interaction, (ii) is highly robust to offset and rf-pulse length and amplitude, and (iii) is very simple to set up. These factors make SLP ideally suited to widespread, non-specialist use in solid-state NMR analyses of nitrogen-containing materials.

Solid State Nuclear Magnetic Resonance, 2019

R = 62.5 kHz. (a) 1D simulated spectrum with a Dirac single pulse. (b-d) projections onto the 195... more R = 62.5 kHz. (a) 1D simulated spectrum with a Dirac single pulse. (b-d) projections onto the 195 Pt axis of 1 H-{ 195 Pt} D-HMQC 2D constant-time spectra recorded with (b) hard-pulse and (c) D (ν 1 = 200 kHz, t p /t tot = 1.25 µs), (d) SLP (ν 1 = 42 kHz, t p = 24 µs).

Phys. Chem. Chem. Phys., 2017

Correction for ‘Analysis of local molecular motions of aromatic sidechains in proteins by 2D and ... more Correction for ‘Analysis of local molecular motions of aromatic sidechains in proteins by 2D and 3D fast MAS NMR spectroscopy and quantum mechanical calculations’ by Piotr Paluch et al., Phys. Chem. Chem. Phys., 2015, 17, 28789–28801.

Solid state nuclear magnetic resonance, Jan 26, 2017

In this work for the first time we show the power of solid state NMR spectroscopy in structural a... more In this work for the first time we show the power of solid state NMR spectroscopy in structural analysis of alumina and catalysts supported on the alumina surface employing very fast (60kHz) magic angle spinning (MAS) technique. In the methodological part we demonstrate that under such MAS condition, cross-polarization (CP) from proton to aluminum is an efficient process when a very weak (27)Al RF field is applied. The mechanism of CP transfer and the Hartmann-Hahn (H-H) matching conditions were tested for (27)Al RF fields equal to 3.3 and 8.3kHz. It has been found that double quantum (DQ) CP/MAS is the best choice for H-H set with RF =3.3kHz. It has been also proved that the quality of (1)H-(27)Al CP/MAS spectra strongly depends on (27)Al carrier offset. Applied to γ-alumina, this method revealed that (1)H-(27)Al CP/MAS at 60kHz is extremely useful for mapping the distribution of hydroxyl groups on the surface. Indeed, the AlV sites, which are not easily detected with Single Pulse ...

Solid state nuclear magnetic resonance, 2017

We present an NMR methodology which can be used to study the dynamical processes occurring in org... more We present an NMR methodology which can be used to study the dynamical processes occurring in organophosphorus compounds that belong to the group of the organic ionic plastic crystals (OIPCs). As model samples we employed two phosphonium tetrafluoroborate salts; (t-Bu)3PH(+)BF4(-) (1) and (Me)3PH(+)BF4(-) (2). Both samples possess in their structures direct H-P bonds, and both undergo complex thermal processes in the solid state, forming below the melting point three or four phases, respectively. (1)H-(31)P CPVC (Cross-Polarization Variable Contact) measurements were performed under Very Fast Magic Angle Spinning with speed equal to 50 or 60 kHz, in order (i) to establish the hydrogen-phosphorus dipolar couplings, and (ii) to correlate the dipolar splitting values with molecular motions of the cation. Our project is divided into three sections. In the first part we present DSC studies of (1) and (2), to verify whether these samples fulfill the requirements that define them as OIPC. ...

Crystal Growth & Design, 2016

Journal of Pharmaceutical Sciences, 2015

In this work, for the first time we report complementary structural and spectral studies of linez... more In this work, for the first time we report complementary structural and spectral studies of linezolid and its synthetic precursors (R)-N-{3-[3-fluoro-4-(morpholin-4-yl)phenyl]-2-oxooxazolidin-5-yl}methanol and (R)-N-{3-[3-fluoro-4-(morpholin-4-yl)phenyl]-2-oxooxazolidin-5-yl}methyl azide employing solid-state nuclear magnetic resonance (SS NMR) spectroscopy and electron ionization mass spectrometry. Each technique provides unique and specific set of information. Through high-resolution SS NMR using (13) C, (15) N, and (19) F as structural probes, we revealed dynamic molecular disorder in the crystal lattice for polymorphs II and III of linezolid, never reported before. Utilizing variable temperature (13) C cross-polarization magic-angle spinning technique, we proved that the disorder has a local character. Only morpholine residue of linezolid is under fast regime exchange at room temperature. This process slows down at a lower temperature and stopped at 213 K. The mass spectrometry revealed that chemical modification at oxazolidinone end of linezolid has a significant influence on fragmentation pathways of studied drug and its synthetic precursors. In particular, the compound that has azide group at the methyl substituent in the position C5 of the oxazolidinone ring is characterized by the most complicated fragmentation pattern, probably caused by thermal decomposition, which was taking place before ionization. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.

The Journal of Physical Chemistry C, 2015

Magnetic Resonance in Chemistry, 2014

Annual Reports on NMR Spectroscopy, 2014

Contents 1. Introduction 2. Development of the New Solid-State NMR Techniques Useful in Structura... more Contents 1. Introduction 2. Development of the New Solid-State NMR Techniques Useful in Structural Studies of Peptides 2.1 1 H Solid-State NMR 2.2 13 C and 15 N Sensitivity under Fast and Medium Magic-Angle Spinning 2.3 Two-Dimensional Correlations under F-MAS 2.4 Quadrupolar Nuclei 3. Molecular Dynamics of Peptides in the Solid State 3.1 Probing the Dynamics in Different Time Scales 3.2 Tools for Analysis of the Local Molecular Motions of Peptides in the Solid State 4. Polymorphism and Solvatomorphism of Peptides 4.1 Solid-State NMR Study of Polymorphs and Solvatomorphs 5. Complementarity of Theoretical and NMR Methods in Assignment of the Solid-State Structure of Peptides 5.1 Techniques Used for Calculations of NMR Parameters in the Solid State 5.2 Theoretical Methods as a Tool for Structure Assignment of Peptides in the Solid State 5.3 Fine Refinement of Peptide Crystals with Molecular Disorder 5.4 Theoretical Methods Versus Molecular Motion 6. Concluding Remarks Acknowledgement References

The Journal of Physical Chemistry B, 2013

Thermal reactions in two Tyr-Ala-Phe (YAF) tripeptide crystals with different molecular packing (... more Thermal reactions in two Tyr-Ala-Phe (YAF) tripeptide crystals with different molecular packing (monoclinic and hexagonal), distinct stereochemistry of central amino acid (D or L alanine) and specific arrangement of molecules in the crystal lattice (head-totail) were investigated. Samples were heated up to 180°C, while the melting point for YAF crystals is above the 220°C. Below the melting temperature, in both cases the chemical reactions leading to formation of cyclic dipeptides (YA diketopiperazine) and leaving of phenylalanine were observed. Two possible mechanisms of chemical reaction in the crystal lattice assuming intra-and/or intermolecular pathways were considered. 13 C and 15 N enriched YAF samples were employed to study of mechanism of solid state reactivity using mass spectrometry and advanced solid state NMR techniques (2D DARR (Dipolar Assisted Rotational Resonance) and 2D Double CP (Cross-Polarization) correlations).

Solid State Nuclear Magnetic Resonance, 2009

Ni(II) with bis(acetylacetone)ethylenediamine ligand forms complexes which crystallizes as semihy... more Ni(II) with bis(acetylacetone)ethylenediamine ligand forms complexes which crystallizes as semihydrate with C2/c space group in monoclinic system and anhydrous form with Pna2(1) space group in orthorhombic system. 13 C and 15 N CP/MAS experiments were employed for structural characterization of both forms and searching of process of reversible water exchange in the crystal lattice. Comparative analysis of 13 C and 15 N principal elements of chemical shift tensors for ligand and complexes showed the sensitivity of d ii elements both for complexation and phase reaction processes. Theoretical 13 C and 15 N NMR shielding parameters s ii were computed employing ONIOM approach and correlated with experimental d ii data. The applicability of ONIOM in structural analysis of coordination compounds (CC) is discussed.

Macromolecular Symposia, 2014

In the first part of article, the "NMR Crystallography" approach as tool to fine refinement of so... more In the first part of article, the "NMR Crystallography" approach as tool to fine refinement of solid state structure of biopolymers is presented, employing the a polymorph of L-polylactide (PLLA) as model. Slow Magic Angle Spinning (MAS) technique (with spinning rate of sample in range from 1.2 kHz to 8.0 kHz) was used to assign 13 C isotropic chemical shifts and values of 13 C d ii principal elements of chemical shifts tensors (CST). Theoretical 13 C shielding parameters s ii were obtained employing GIPAW (Gauge Invariant Projector Augmented Wave) method and compared with experimental 13 C d ii elements. The computed and experimental 13 C CP/MAS spectra for WAND (Wide Angle Neutron Diffraction) geometry of powdered a PLLA were evaluated. It was revealed that the computed model of a PLLA model better fit to experimental NMR spectra.In the second part of article the applications of the new NMR methodology, so called very fast MAS (VF MAS) with sample spinning over 60 kHz are presented. The power of this approach is shown employing the 13 C and 15 N labeled protein, ubiquitin. We revealed that Cross-Polarization with Variable Contact (CPVC) time sequence under very-fast MAS condition performed in two-dimensional (2D) mode is very efficient method to measure accurately the CÀ ÀH and NÀ ÀH distances, and to analyze the dynamics of proteins with overlapped resonances in aliphatic and aromatic regions.

Journal of Magnetic Resonance, 2013

We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-V... more We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-VC), is very efficient at ultra-fast MAS (ν R ≥ 60 kHz) to measure accurately the C-H and N-H distances, and to analyze the dynamics of bio-molecules. This experiment can be performed with samples that are either 13 C or 15 N labeled or without any labeling. The method is very robust experimentally with respect to imperfect Hartman-Hahn setting, and presents a large scaling factor allowing a better dipolar determination, especially for long C-H or N-H distances, or for CH 3 or NH 3 moieties with three-site hopping. At ultra-fast MAS, it can be used quantitatively in a 2D way, because its scaling factor is then little dependent on the offsets. This robustness with respect to offset is related to the ultra-fast spinning speed, and hence to the related small rotor diameter. Indeed, these two specifications lead to efficient n = ±1 zero-quantum Hartman-Hahn CP-transfers with large rf-fields on proton and carbon or nitrogen channels, and large dipolar scaling factor.  R = 60 kHz,  1H = 100 kHz,  1C = 160 kHz. Slices along F1 are shown for signals at: either 123.7 (b) or 125.1 ppm (c), with aromatic CH residues of Tyr and Phe, respectively. The phenyl ring of Tyr is static, while that of Phe residue undergoes fast molecular motions. Schematic drawing of the pulse sequences used in this work for measuring X-1 H dipolar couplings: (a) CP-VC, (b) CP-PI, and (c) PISEMA. Meaning of abbreviations: CT-contact time, VCT-variable contact time, PI-phase inversion, SEMA-Spin Exchange at the Magic Angle.