Infrared spectra and the structure of salts of imidazoles

Epishina, L. V.; Slovetskii, V. I.; Osipov, V. G.; Lebedev, O. V.; Khmel'nitskii, L. I.; Sevost'yanova, V. V.; Новикова, Т. С.

doi:10.1007/bf00481609

Cited by 8 publications

(7 citation statements)

References 14 publications

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“…Next, turning to the Amide‐II band, the lowest frequency feature at 1496–7 cm −1 corresponds to aromatic ring stretching modes of the indole or imidazole groups, dominated by tryptophan or histidine, with a greater intensity in the Ext‐matrix. [44,49,50] The band at 1512–3 cm −1 arises from the antiparallel β‐sheet secondary structure, also with higher intensity in the Ext‐matrix, and is consistent with the antiparallel β‐sheet bands found in the Amide‐I regions. In contrast, the third contributing band at 1525–8 cm −1 arises from parallel β‐sheet secondary structure and shows a greater intensity for the macrofibrils (also in agreement with the Amide‐I band deconvolution).…”

Section: Discussionsupporting

confidence: 71%

“…Also, given are the assignments of the deconvoluted bands based on well‐established data from the literature. [31,32,49–52] Figure 4 shows the constituent bands from the Ext‐matrix and macrofibril spectra shown in Figure 3 presented in block format, that is representing the integrated band intensities. This demonstrates the clear spectral difference between the two regions, with 3 of the assigned bands only being present in 1 of the 2 spectra and the others showing relative intensity shifts.…”

Section: Resultsmentioning

confidence: 99%

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Chemically characterizing the cortical cell nano‐structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM‐IR)

Fellows

Casford

Davies

2021

Intern J of Cosmetic Sci

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Objective The use of conventional microscopy and vibrational spectroscopy in the optical region to investigate the chemical nature of hair fibres on a nanometre scale is frustrated by the diffraction limit of light, prohibiting the spectral elucidation of nanoscale sub‐structures that contribute to the bulk properties of hair. The aim of this work was to overcome this limitation and gain unprecedented chemical resolution of cortical cell nano‐structure of hair. Methods The hybrid technique of AFM‐IR, combining atomic force microscopy with an IR laser, circumvents the diffraction limit of light and achieves nanoscale chemical resolution down to the AFM tip radius. In this work, AFM‐IR was employed on ultra‐thin microtomed cross‐sections of human hair fibres to spectrally distinguish and characterize the specific protein structures and environments within the nanoscale components of cortical cells. Results At first, a topographical and chemical distinction between the macrofibrils and the surrounding intermacrofibillar matrix was achieved based on 2.5 × 2.5 μm maps of cortical cell cross‐sections. It was found that the intermacrofibrillar matrix has a large protein content and specific cysteine‐related residues, whereas the macrofibrils showed bigger contributions from aliphatic amino acid residues and acidic‐/ester‐containing species (e.g. lipids). Localized spectra recorded at a spatial resolution of the order of the AFM tip radius enabled the chemical composition of each region to be determined following deconvolution of the Amide‐I and Amide‐II bands. This provided specific evidence for a greater proportion of α‐helices in the macrofibrils and correspondingly larger contributions of β‐sheet secondary structures in the intermacrofibrillar matrix, as inferred in earlier studies. Analysis of the parallel and antiparallel β‐sheet structures, and of selected dominant amino acid residues, yielded further novel composition and conformation results for both regions. Conclusion In this work, we overcome the diffraction limit of light using atomic force microscopy integrated with IR laser spectroscopy (AFM‐IR) to characterize sub‐micron features of the hair cortex at ultra‐high spatial resolution. The resulting spectral analysis shows clear distinctions in the Amide bands in the macrofibrils and surrounding intermacrofibrillar matrix, yielding novel insight into the molecular structure and intermolecular stabilization interactions of the constituent proteins within each cortical component.

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Section: Discussionsupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Chemically characterizing the cortical cell nano‐structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM‐IR)

Fellows

Casford

Davies

2021

Intern J of Cosmetic Sci

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“…The intensity profiles based on the deconvoluted spectra in Figure 4 can be found in Figure 5 where three separate spectral regions (Amide‐II, Amide‐I and >1700 cm −1 ) have been separated from each other and normalised independently (the bands >1700 cm −1 are also shown in the Amide‐I profiles for comparison). These profiles, along with the assignments given in Table 2 from the literature, 41–45 can be used to analyse the variations in contributing species for each of the features investigated and as discussed in the following sections.…”

Section: Resultsmentioning

confidence: 99%

“…The band at 1495 cm −1 corresponds to the C‐N in‐ring stretching mode arising predominantly from the His/Trp residues 43,44 . This feature appears uniformly across the different medulla components but with a greater intensity in the cortex, indicating there is a lower amount within the medulla.…”

Section: Resultsmentioning

confidence: 99%

Using hybrid atomic force microscopy and infrared spectroscopy (AFM‐IR) to identify chemical components of the hair medulla on the nanoscale

Fellows

Casford

Davies

2021

Journal of Microscopy

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Atomic force microscopy integrated with infrared spectroscopy (AFM‐IR) has been used to topographically and chemically examine the medulla of human hair fibres with nanometre scale lateral resolution. The mapping of cross‐sections of the medulla showed two distinct structural components which were subsequently characterised spectroscopically. One of these components was shown to be closely similar to cortical cell species, consistent with the fibrillar structures found in previous electron microscope (EM) investigations. The other component showed large chemical differences from cortical cells and was assigned to globular vacuole species, also confirming EM observations. Further characterisation of the two components was achieved through spectral deconvolution of the protein Amide‐I and ‐II bands. This showed that the vacuoles have a greater proportion of the most thermodynamically stable conformation, namely the antiparallel β‐sheet structures. This chimes with the observed lower cysteine concentration, indicating a lower proportion of restrictive disulphide cross‐link bonding. Furthermore, the large α‐helix presence within the vacuoles points to a loss of matrix‐like material as well as significant intermolecular stabilisation of the protein structures. By analysing the carbonyl stretching region, it was established that the fibrillar, cortical cell‐like components showed considerable stabilisation from H‐bonding interactions, similar to the cortex, involving amino acid side chains whereas, in contrast, the vacuoles were found to only be stabilised significantly by structural lipids.

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“…Results from impact sensitivity, friction sensitivity time-to-explosion temperature and vacuum stability tests indicate that 2,4-dinitroimidazole is less sensitive than both RDX and HMX [21, 22]. On comparison with 2,4-dinitroimidazole itself, the studies on its metal salts are rare, particularly their molecular structures [23-26]. Only its copper salt [Cu(DNI) 2 (H 2 O) 2 ]·3H 2 O has been characterized by single-crystal X-ray diffraction analysis and revealed that it is a distorted four-coordinate planar geometry [26].…”

Section: Introductionmentioning

confidence: 99%

Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

et al. 2009

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Compound 1 contains two isolated nickel centers in its structure, one being six-coordinate and another five-coordinate. The structure of 2 contains a lead (II) center surrounded by two chelating DNI ligands and four water molecules in distorted square-antiprism geometry. The abundant hydrogen bonds in two compounds link the molecules into three-dimensional network and stabilize the molecules. The TG-DSC analysis reveals that the first step is the loss of water molecules and the final residue is the corresponding metal oxides and carbon.

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Infrared spectra and the structure of salts of imidazoles

Cited by 8 publications

References 14 publications

Chemically characterizing the cortical cell nano‐structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM‐IR)

Chemically characterizing the cortical cell nano‐structure of human hair using atomic force microscopy integrated with infrared spectroscopy (AFM‐IR)

Using hybrid atomic force microscopy and infrared spectroscopy (AFM‐IR) to identify chemical components of the hair medulla on the nanoscale

Crystal Structures and Thermal Properties of Two Transition-Metal Compounds {[Ni(DNI)2(H2O)3][Ni(DNI)2 (H2O)4]}·6H2O and Pb(DNI)2(H2O)4 (DNI = 2,4-Dinitroimidazolate)

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