Real-Time Synchrotron Small-Angle X-ray Scattering Studies of Collagen Structure during Leather Processing

Zhang, Yi; Ingham, Bridget; Cheong, Soshan; Ariotti, Nicholas; Tilley, Richard D.; Naffa, Rafea; Holmes, Geoff; Clarke, David J.; Prabakar, Sujay

doi:10.1021/acs.iecr.7b03860

Cited by 24 publications

(25 citation statements)

References 28 publications

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“…Looseness is a major concern to the leather industry in terms of its effect on structure of the leather and appearance of the final leather product [6]. At present looseness can only be accurately identified once the leather is dried, thus tanners can only address it by either discarding the leather or remedial treatment, costing both time and money [7][8][9]. There is an understanding that looseness is prevalent in specific regions including the shoulder and flanks whereas other regions such as the backbone and official sampling position (OSP) are typically unaffected.…”

Section: Introductionmentioning

confidence: 99%

Raman and Atr-Ftir Spectroscopy Towards Classification of Wet Blue Bovine Leather Using Ratiometric and Chemometric Analysis

et al. 2020

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There is a substantial loss of value in bovine leather every year due to a leather quality defect known as "looseness". Data show that 7% of domestic hide production is affected to some degree, with a loss of $35 m in export returns. This investigation is devoted to gaining a better understanding of tight and loose wet blue leather based on vibrational spectroscopy observations of its structural variations caused by physical and chemical changes that also affect the tensile and tear strength. Several regions from the wet blue leather were selected for analysis. Samples of wet blue bovine leather were collected and studied in the sliced form using Raman spectroscopy (using 532 nm excitation laser) and Attenuated Total Reflectance-Fourier Transform InfraRed (ATR-FTIR) spectroscopy. The purpose of this study was to use ATR-FTIR and Raman spectra to classify distal axilla (DA) and official sampling position (OSP) leather samples and then employ univariate or multivariate analysis or both. For univariate analysis, the 1448 cm − 1 (CH 2 deformation) band and the 1669 cm − 1 (Amide I) band were used for evaluating the lipid-to-protein ratio from OSP and DA Raman and IR spectra as indicators of leather quality. Curve-fitting by the sums-of-Gaussians method was used to calculate the peak area ratios of 1448 and 1669 cm − 1 band. The ratio values obtained for DA and OSP are 0.57 ± 0.099, 0.73 ± 0.063 for Raman and 0.40 ± 0.06 and 0.50 ± 0.09 for ATR-FTIR. The results provide significant insight into how these regions can be classified. Further, to identify the spectral changes in the secondary structures of collagen, the Amide I region (1600-1700 cm − 1) was investigated and curve-fitted-area ratios were calculated. The 1648:1681 cm − 1 (non-reducing: reducing collagen types) band area ratios were used for Raman and 1632:1650 cm − 1 (triple helix: α-like helix collagen) for IR. The ratios show a significant difference between the two classes. To support this qualitative analysis, logistic regression was performed on the univariate data to classify the samples quantitatively into one of the two groups. Accuracy for Raman data was 90% and for ATR-FTIR data 100%. Both Raman and ATR-FTIR complemented each other very well in differentiating the two groups. As a comparison, and to reconfirm the classification, multivariate analysis was performed using Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). The results obtained indicate good classification between the two leather groups based on protein and lipid content. Principal component score 2 (PC2) distinguishes OSP and DA by symmetrically grouping samples at positive and negative extremes. The study demonstrates an excellent model for wider research on vibrational spectroscopy for early and rapid diagnosis of leather quality.

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Section: Introductionmentioning

confidence: 99%

Raman and Atr-Ftir Spectroscopy Towards Classification of Wet Blue Bovine Leather Using Ratiometric and Chemometric Analysis

et al. 2020

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“…To study the role of the solvent in Cr uptake as an event independent of fixation, we conducted SAXS measurements prior to basification. The characteristic scattering from the leather samples is from the long-range order of collagen molecules present in a quarter-staggered arrangement, with repeating gap/overlap regions in a characteristic axial periodicity (D-period) [16,17]. The scattering profiles for pickled hide treated in both propylene carbonate (PC-0%) and conventional (WT-0%) solvents were similar to each other and exhibited the typical isotropic collagen X-ray diffraction patterns of bovine hide, displaying a series of Bragg peaks arising from the long-range ordered collagen structure [16].…”

Section: Saxs Peak Changes With Tanningmentioning

confidence: 99%

“…The characteristic scattering from the leather samples is from the long-range order of collagen molecules present in a quarter-staggered arrangement, with repeating gap/overlap regions in a characteristic axial periodicity (D-period) [16,17]. The scattering profiles for pickled hide treated in both propylene carbonate (PC-0%) and conventional (WT-0%) solvents were similar to each other and exhibited the typical isotropic collagen X-ray diffraction patterns of bovine hide, displaying a series of Bragg peaks arising from the long-range ordered collagen structure [16]. On tanning with chromium sulphate (2% to 8%) for both PC and WT samples, significant changes in the relative diffraction intensities of the Bragg peaks were observed, indicating that the internal molecular structure of collagen had changed during tanning.…”

Section: Saxs Peak Changes With Tanningmentioning

confidence: 99%

“…Collagen molecules are aligned in a quarter stagger structure, resulting in repeating gap/overlap regions within the fibrils [12,13]. Because of its ordered arrangement, molecular level information can be acquired by Xray scattering techniques, including diffraction, to measure the periodicity of the gap/overlap regions (D-period) and the size of collagen fibrils [14][15][16][17][18][19]. The interactions between water and collagen play a crucial role in the stability of the triple helix [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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Collagen structure changes during chrome tanning in propylene carbonate

et al. 2019

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Green solvents, such as propylene carbonate (PC), can be used in leather processing to improve the efficiency of chrome tanning and reduce wastewater. Here we report a combined small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) study on PC and its efficacy as a carrier medium during chrome tanning. SAXS analysis on the collagen structure of chrome tanned leather using PC, compared to conventionally tanned leather using water, showed an increase in Cr uptake in addition to the more uniform penetration of Cr through the leather cross-section. The increased binding of Cr to the collagen matrix drives the decreased hydration environment of the collagen triple helix. Furthermore, DSC studies show a uniform hydrothermal stability for the PC samples due to the more even distribution of Cr through the collagen matrix. Understanding the mechanisms by which chrome tanning occurs in non-aqueous solvents can guide us towards a more sustainable future for the leather industry.

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“…However, chrome tanning causes a decrease in the quantity of all three natural crosslinks. During chrome tanning, the carboxylate (−COO − ) groups of aspartic (Asp) and glutamic (Glu) acid residues of collagen are bonded covalently [7], causing significant structural changes in collagen [40,41]. Similarly, the removal of structure stabilizing natural crosslinks can also cause changes in the collagen structure [3,42].…”

Section: Quantification Of Natural Crosslinks In Skin Collagen: Relatmentioning

confidence: 99%

Quantitative and structural analysis of isotopically labelled natural crosslinks in type I skin collagen using LC-HRMS and SANS

et al. 2019

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Collagen structure in biological tissues imparts its intrinsic physical properties by the formation of several covalent crosslinks. For the first time, two major crosslinks in the skin dihydroxylysinonorleucine (HLNL) and histidinohydroxymerodesmosine (HHMD), were isotopically labelled and then analysed by liquid-chromatography high-resolution accurate-mass mass spectrometry (LC-HRMS) and small-angle neutron scattering (SANS). The isotopic labelling followed by LC-HRMS confirmed the presence of one imino group in both HLNL and HHMD, making them more susceptible to degrade at low pH. The structural changes in collagen due to extreme changes in the pH and chrome tanning were highlighted by the SANS contrast variation between isotopic labelled and unlabelled crosslinks. This provided a better understanding of the interaction of natural crosslinks with the chromium sulphate in collagen suggesting that the development of a benign crosslinking method can help retain the intrinsic physical properties of the leather. This analytical method can also be applied to study artificial crosslinking in other collagenous tissues for biomedical applications.

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Real-Time Synchrotron Small-Angle X-ray Scattering Studies of Collagen Structure during Leather Processing

Cited by 24 publications

References 28 publications

Raman and Atr-Ftir Spectroscopy Towards Classification of Wet Blue Bovine Leather Using Ratiometric and Chemometric Analysis

Raman and Atr-Ftir Spectroscopy Towards Classification of Wet Blue Bovine Leather Using Ratiometric and Chemometric Analysis

Collagen structure changes during chrome tanning in propylene carbonate

Quantitative and structural analysis of isotopically labelled natural crosslinks in type I skin collagen using LC-HRMS and SANS

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