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Abstract: We proved the ability of Fourier Transform Infrared microspectroscopy (microFTIR) complemented by Principal Component Analysis (PCA) to detect protein phosphorylation/de-phosphorylation in mammalian cells. We analyzed by microFTIR human polymorphonuclear neutrophil (PMNs) leukocytes, mouse-derived parental Ba/F3 cells (Ba/F3#PAR), Ba/F3 cells transfected with p210BCR/ABL (Ba/F3#WT) and expressing high levels of protein tyrosine kinase (PTK), and human-derived BCR/ABL positive K562 leukemic cell sub-clones engineered to differently express receptor-type tyrosine-protein phosphatase gamma (PTPRG). Synchrotron radiation (SR) and conventional (globar) IR sources were used to perform microFTIR respectively, on single cells and over several cells within the same sample. Ex vivo time-course experiments were run, inducing maximal protein phosphorylation in PMNs by 100 nM N-formylated tripeptide fMLP. Within the specific IR fingerprint 1800–850 cm−1 frequency domain, PCA identified two regions with maximal signal variance. These were used to model and test the robustness of PCA in representing the dynamics of protein phosphorylation/de-phosphorylation processes. An IR signal ratio marker reflecting the homeostatic control by protein kinases and phosphatases was identified in normal leukocytes. The models identified by microFTIR and PCA in normal leukocytes also distinguished BCR/ABL positive Ba/F3#WT from BCR/ABL negative Ba/F3#PAR cells as well as K562 cells exposed to functionally active protein tyrosine phosphatase recombinant protein ICD-Tat transduced in cells by HIV-1 Tat technology or cells treated with the PTK inhibitor imatinib mesylate (IMA) from cells exposed to phosphatase inactive (D1028A)ICD-Tat recombinant protein and untreated control cells, respectively. The IR signal marker correctly reflected the degrees of protein phosphorylation associated with abnormal PTK activity in BCR/ABL positive leukemic cells and in general was inversely related to the expression/activity of PTPRG in leukemic sub-clones. In conclusion, we have described a new, reliable and simple spectroscopic method to study the ex vivo protein phosphorylation/de-phosphorylation balance in cell models: it is suitable for biomedical and pharmacological research labs but it also needs further optimization and its evaluation on large cohorts of patients to be proposed in the clinical setting of leukemia.

Open Access

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Abstract: Synchrotron radiation (SR) IR microspectroscopy has enabled determination of the thermodynamics, kinetics, and molecular orientation of CO2 adsorbed in single microcrystals of a functionalized metal–organic framework (MOF) under conditions relevant to carbon capture from flue gases. Single crystals of the small-pore MOF, Sc2(BDC-NH2)3, (BDC-NH2=2-amino-1,4-benzenedicarboxylate), with well-defined crystal form have been investigated during CO2 uptake at partial pressures of 0.025-0.2 bar at 298–373 K. The enthalpy and diffusivity of adsorption determined from individual single crystals are consistent with values obtained from measurements on bulk samples. The brilliant SR IR source permits rapid collection of polarized spectra. Strong variations in absorbance of the symmetric stretch of the NH2 groups of the MOF and the asymmetric stretch of the adsorbed CO2 at different orientations of the crystals relative to the polarized IR light show that CO2 molecules align along channels in the MOF.

Open Access

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Abstract: We report here on a first study using synchrotron radiation-based Fourier transform infrared microspectroscopy and imaging to investigate HT1080 human fibrosarcoma cells grown onto different-aged type I collagen networks. Spectral images were analyzed with k-means and fuzzy C-means (FCM) clustering algorithms. K-means delineated tumor cells from their surrounding collagen networks and the latter as a function of age mainly due to specific changes in the sugar absorption region. The FCM analysis gave a better nuance of the spectral images. A progression of the biochemical information was observed upon going from the cellular compartments to the pericellular contact regions and to the intact collagens of the different age groups. Two spectral markers based on sugar and protein bands via the intensity ratio (I1032/I1655) and band area ratio (Asugar/Aamide II), showed an increase in advanced glycation end products (AGEs) with age. A clear-separation of the three age groups was obtained for spectra originating from the peripheral contact areas mainly due to changes in protein band intensities. The above-described markers decreased to constant levels for the three conditions indicating a masking of the biochemical information. These results hold promises to better understand the impact of age on tumor progression processes while highlighting new markers of the tumor cell invasion front.

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Abstract: We present an unambiguous identification of low-frequency terahertz vibrations in the archetypal imidazole-based metal-organic framework (MOF) materials: ZIF-4, ZIF-7, and ZIF-8, all of which adopt a zeolite-like nanoporous structure. Using inelastic neutron scattering and synchrotron radiation far-infrared absorption spectroscopy, in conjunction with density functional theory (DFT), we have pinpointed all major sources of vibrational modes. Ab initio DFT calculations revealed the complex nature of the collective THz modes, which enable us to establish detailed correlations with experiments. We discover that low-energy conformational dynamics offers multiple pathways to elucidate novel physical phenomena observed in MOFs. New evidence demonstrates that THz modes are intrinsically linked, not only to anomalous elasticity underpinning gate-opening and pore-breathing mechanisms, but also to shear-induced phase transitions and the onset of structural instability.

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Abstract: The mechanical properties of graphene oxide (GO) paper are critically defined both by the mechanical properties of the constituent GO sheets and the interaction between these sheets. Functional carbonyl and carboxyl groups decorating defects, expected to be predominantly sheet edges of the GO, are shown to transfer forces to the in-plane carbon–carbon bonding using a novel technique combining atomic force microscopy (AFM) to mechanically deform discrete volumes of GO materials while synchrotron Fourier-transform infra-red (FTIR) microspectroscopy evaluated molecular level bond deformation mechanisms of the GO. Spectroscopic absorption peaks corresponding to in-plane aromatic C[double bond, length as m-dash]C bonds from GO sheets were observed to shift during tensile tests. Importantly, FTIR provided information on clear absorption peak shifts from C[double bond, length as m-dash]O bonds linking along the GO sheet edges, indicating transfer of forces between both C[double bond, length as m-dash]C and C[double bond, length as m-dash]O bonds during tensile deformation. Grüneisen parameters were used to quantitatively link the macroscopic FTIR peak shifts to molecular level chemical bond strains, with relatively low bond strains prevalent when applying external forces to the GO paper suggesting probing of hydrogen bonding interactions. We propose a mechanistic description of molecular interactions between GO sheets in the paper from these experiments, which is important in future strategies for further modification and improvement of GO-based materials.