Bijaylaxmi Patra (Centre of Biomedical Research, India)
LinkedIn: @Bijaylaxmi Patra; X: @BijaylaxmiNMR; Bluesky: @bijaylaxmi.bsky.social
Abstract: Fast magic angle spinning (MAS) is a powerful technique in solid-state nuclear magnetic resonance (ssNMR) spectroscopy that effectively decreases line broadening and enables high-resolution structural study of biological systems. Nevertheless, its utility in probing complex and heterogeneous biomaterials in their native form has been constrained. In this study, we leveraged fast MAS (70KHz) to perform 2D ¹H-detected ¹³C–¹H double cross-polarization (CP) heteronuclear correlation experiments on native bone. This high-resolution method enabled the detection of previously unobserved inter-residue correlations within the aliphatic region of collagen. Additionally, our findings suggest potential π-interactions between aromatic amino acids and spatially proximal anionic or imino acids within the collagen triple helix. Our study paves the way for advanced ¹H-detected heteronuclear correlation experiments under fast MAS to more effectively elucidate the complex and heterogeneous structural organization of other native collagen-rich biological systems.
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Hello Patra, nice presentation!
I was wondering if you can observe the same inter-residue correlation also exploiting other SS-NMR experiments such as the C-C DARR or similar.-
Hi Marco, thanks for showing interest in my work.
Yes, we may observe the same inter-residue correlations using other ssNMR experiments as well, and our future plans include performing such experiments to obtain ¹³C–¹³C correlations.
However, as an initial study, we preferred ¹H-detected ¹³C–¹H experiments because they require significantly less experimental time compared to ¹³C–¹³C correlation experiments, especially since the experiments are conducted at natural isotopic abundance.Fast MAS techniques have not been widely used to study collagen in native bone due to concerns about friction-induced sample instability during long experimental durations. In our previous study (https://doi.org/10.1002/mrc.5508), we demonstrated the feasibility of acquiring ¹H–¹H correlations. Building on that, we now report ¹³C–¹H correlations, and we believe that ¹³C–¹³C experiments will be even more interesting in future studies.
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Hi Marco, thanks for showing interest in my work.
Yes, we may observe the same inter-residue correlations using other ssNMR experiments as well, and our future plans include performing such experiments to obtain ¹³C–¹³C correlations.
However, as an initial study, we preferred ¹H-detected ¹³C–¹H experiments because they require significantly less experimental time compared to ¹³C–¹³C correlation experiments, especially since the experiments are conducted at natural isotopic abundance.Fast MAS techniques have not been widely used to study collagen in native bone due to concerns about friction-induced sample instability during long experimental durations. In our previous study (https://doi.org/10.1002/mrc.5508), we demonstrated the feasibility of acquiring ¹H–¹H correlations. Building on that, we now report ¹³C–¹H correlations, and we believe that ¹³C–¹³C experiments will be even more interesting in future studies.
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Very nice presentation. I was just wondering if it would be interesting to study other components of the bone and how they are structured within the bone e.g the lipids.
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Yes, it is indeed very interesting to study other components in bone, as it is rich in various types of molecules within its extracellular matrix.
Bone is a fascinating biomaterial that my lab has been working on for many years. My seniors have already explored water–lipid interactions (https://doi.org/10.1016/j.ssnmr.2020.101666), water–mineral interactions (https://doi.org/10.1021/acsomega.2c01133), and citrate–collagen interactions within the bone matrix (https://doi.org/10.1021/acs.jpcb.1c01431).
Specifically, regarding lipids in bone, the major type found in the matrix is triglycerides. Nidhi et al. studied lipids in hydrated, dehydrated, and H₂O–D₂O exchanged bone samples. They found that dehydration and H/D exchange significantly affect the transverse relaxation times (T₂) of triglycerides. These changes reflect alterations in the hydrogen bonding network and the local conformational dynamics of the lipid environment. Dehydration increased the mobility of triglycerides, indicating greater freedom of motion when water is removed. For further insights into other components, I recommend reading this book chapter: https://doi.org/10.1039/9781839165702-00614
Thank you for your curiosity and engagement with our research.
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Hi Bijaylakshmi, Thank you for the presentation.
So if I understood correctly, you just ground the native bone and packed it directly into the rotor? Were there any other steps involved in preparing the sample for the fast MAS experiments?
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Studies have shown that cryogenic grinding can alter the structure and hydration of bone. Therefore, we avoided both cryogenic and mechanical grinding. Instead, we carefully prepared small bone flakes (tiny pieces) using a scalpel and directly packed them into the rotor without any further processing. These flakes retained the structural and morphological features of the native intact bone.
For further queries, you can refer to our published article: https://doi.org/10.1002/mrc.5508.
I’m grateful for your interest and curiosity about my work.
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