TY  - JOUR
AB  - 13C and 15N solid-state nuclear magnetic resonance (NMR) combined with dynamic nuclear polarization (DNP) is used to investigate the structure of dye-doped biopolymer-based materials that can be used in amplified spontaneous emission (ASE) experiments. By comparing calligraphic paper prepared from cellulose and scaffolds prepared from chitosan as substrates, differences in the interactions of the carrier material with the dye molecule Calcofluor White are obtained. These are most probably induced by structural changes of the carrier material due to its interaction with water forming hydrogen bonds. Such structural differences may explain the obtained variation of the emission wavelength of Calcofluor White doped on these substrates in ASE experiments.
AU  - Höfler, M.V.*
AU  - Hoinka, N.
AU  - Schäfer, T.*
AU  - Horn, M.*
AU  - Aussenac, F.*
AU  - Fuhrmann-Lieker, T.*
AU  - Gutmann, T.*
C1  - 63333
C2  - 51476
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 21550-21558
TI  - Light amplification materials based on biopolymers doped with dye molecules - structural insights from 15N and 13C solid-state dynamic nuclear polarization.
JO  - J. Phys. Chem. C.
VL  - 125
IS  - 39
PB  - Amer Chemical Soc
PY  - 2021
SN  - 1932-7447
ER  - 

TY  - JOUR
AB  - Sensitivity and resolution together determine the quality of NMR spectra in biological solids. Higher magic angle spinning frequencies yield a more efficient suppression of the coupling network and enable atomic-level investigations of protonated protein samples. On the other hand, truncation effects induced by higher magnetic fields have an impact on the achievable sensitivity and resolution. In this work, we address the question of how the proton dipolar coupling network affects the magnetic field strength-dependent gains in sensitivity and resolution. We find that-beyond the canonical B-0(3/2) dependence-an additional factor of 2 in sensitivity can be achieved for residues embedded in the core of the protein, when the static magnetic field induces a transition from the strong- to the weak-coupling limit. The experiments are carried out using a selectively methyl-protonated ((13)CH3) alpha-spectrin SH3 sample, at magnetic field strengths of 11.75 T (H-1 Larmor frequency of 500 MHz) and 23.5 T (H-1 Larmor frequency of 1 GHz).
AU  - Xue, K.
AU  - Sarkar, R.
AU  - Lalli, D.*
AU  - Koch, B.*
AU  - Pintacuda, G.*
AU  - Tosner, Z.*
AU  - Reif, B.
C1  - 60443
C2  - 49458
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 22631-22637
TI  - Impact of magnetic field strength on resolution and sensitivity of proton resonances in biological solids.
JO  - J. Phys. Chem. C.
VL  - 124
IS  - 41
PB  - Amer Chemical Soc
PY  - 2020
SN  - 1932-7447
ER  - 

TY  - JOUR
AB  - In the last decade, proton detection in magic-angle spinning (MAS) solid-state NMR became a popular strategy for biomolecular structure determination. In particular, probe technology has experienced tremendous progress with smaller and smaller diameter rotors achieving ever higher MAS frequencies. MAS rotation frequencies beyond 100 kHz allow to observe and assign protons in fully protonated samples. In these experiments, resolution is however compromised as homogeneous proton-proton dipolar coupling interactions are not completely averaged out. Using a combination of experiments and simulations, we analyze the MAS frequency-dependent intensities of the 1H,13C methyl correlation peaks of a selectively methyl protonated (CH3) microcrystalline sample of the chicken α-spectrin SH3 domain (α-SH3). Extensive simulations involving nine spins employing the program SIMPSON allow to predict the MAS frequency dependence of the proton intensities. The experimental results are used to validate the simulations. As quantitative measure, we determine the characteristic MAS frequency, which is necessary to obtain >50% of the maximum achievable sensitivity. Our results show that this frequency is site-specific and strongly depends on the local methyl density. We find that the characteristic MAS frequency ranges from as low as 20 kHz up to 324 kHz with the average value of 135 ± 88 kHz for this particular sample at a magnetic field strength of 11.7 T. Inclusion of side chain dynamics in the analysis reduces the average characteristic MAS frequency to 104 ± 68 kHz within the range of 11-261 kHz. In case, >80% of the maximum sensitivity shall be achieved, MAS rotation frequencies of 498 ± 370 and 310 ± 227 kHz are required with and without including side chains dynamics in the analysis, respectively.
AU  - Xue, K.
AU  - Sarkar, R.
AU  - Motz, C.*
AU  - Asami, S.*
AU  - Decker, V.*
AU  - Wegner, S.*
AU  - Tosner, Z.*
AU  - Reif, B.
C1  - 55457
C2  - 46163
SP  - 16437-16442
TI  - Magic-angle spinning frequencies beyond 300 kHz are necessary to yield maximum sensitivity in selectively methyl protonated protein samples in solid-state NMR.
JO  - J. Phys. Chem. C.
VL  - 122
IS  - 28
PY  - 2018
SN  - 1932-7447
ER  -