Solid state NMR of isotope labelled murine fur: a powerful tool to study atomic level keratin structure and treatment effects

Abstract

We have prepared mouse fur extensively 13C,15N-labelled in all amino acid types enabling application of 2D solid state NMR techniques which establish covalent and spatial proximities within, and in favorable cases between, residues. 13C double quantum–single quantum correlation and proton driven spin diffusion techniques are particularly useful for resolving certain amino acid types. Unlike 1D experiments on isotopically normal material, the 2D methods allow the chemical shifts of entire spin systems of numerous residue types to be determined, particularly those with one or more distinctively shifted atoms such as Gly, Ser, Thr, Tyr, Phe, Val, Leu, Ile and Pro. Also the partial resolution of the amide signals into two signal envelopes comprising of α-helical, and β-sheet/random coil components, enables resolution of otherwise overlapped α-carbon signals into two distinct cross peak families corresponding to these respective secondary structural regions. The increase in resolution conferred by extensive labelling offers new opportunities to study the chemical fate and structural environments of specific atom and amino acid types under the influence of commercial processes, and therapeutic or cosmetic treatments.Electronic supplementary materialThe online version of this article (doi:10.1007/s10858-016-0056-7) contains supplementary material, which is available to authorized users.

Sex-related chemical differences in keratin from fingernail plates: a solid-state carbon-13 NMR study

“…1A) are similar to the nail spectrum reported previously 26 and to the spectra of other a-keratin containing materials. 8,27,28,33,[36][37][38][39][40][41][42][43] They can be subdivided into four regions at 0-50, 50-80, 105-163 and 163-186 ppm, comprising side-chain aliphatic, C a -methine, side-chain aromatic and carbonyl signals, respectively. This partition is not completely strict, because the rst region contains a C a peak of Gly, while the second one comprises C b peaks of Ser and Thr.…”

“…In the side-chain aromatic range, there are three amino acid signals and many disturbing sidebands. The detailed assignment of the tted signals based on the former publications 8,33,43 and Biological Magnetic Resonance Data Bank 48 is presented in Table 1.…”

“…A most promising method of structural analysis of complex, solid, native biological materials is solid-state NMR spectroscopy (ssNMR). 8,[30][31][32][33] Classical high-resolution 13 C ssNMR requires fast magic-angle spinning (MAS) with high-power decoupling to narrow the 13 C peaks and cross-polarization (CP) to increase their intensity. 34,35 This method has already provided a lot of information on keratin at all its structural levels and on keratin molecular mobility.…”

“…In particular, previous 13 C CP/MAS NMR papers have been devoted to the interpretation of the carbon-13 spectra, characterization of native and modied keratins, elucidation of the a-keratin structure, testing its dependence on stretching, heating and chemical treatment, analysis of the a-helix and b-sheet regions and observation of their mutual transitions, monitoring disulphide bonds breaking under various conditions, thermal and reductive/oxidative denaturation, assessment of crystalline and amorphous regions, characterization of molecular dynamics and so on. 8,[26][27][28]33,[36][37][38][39][40][41][42][43] The studies were made on human and horse hair, human stratum corneum, horse hoof and sheep wool.…”

Processing keratin from camel hair and cashmere with ionic liquids

“…The specific analysis and characterization of these natural biomaterials is therefore of importance. Due to its three dimensional polypeptide structure which consists of a triple-helix of protein chains held together by a range of covalent (disulfide bonds) and noncovalent interactions [33,34], keratin is stable to most solvents. Water soluble keratin from wool, hair, and feathers, can be partially extracted by alkali hydrolysis [35], enzyme-alkaline treatment [36], steam explosion [37] and the Shindai method [38].…”