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Accepted Article

Title: Self-assembled Oligopeptide as a Versatile NMR AlignmentMedium for the Measurements of Residual Dipolar Couplings inMethanol

Authors: Xinxiang Lei, Feng Qiu, Han Sun, Liwen Bai, Wen-XuanWang, Wensheng Xiang, and Hongping Xiao

This manuscript has been accepted after peer review and appears as anAccepted Article online prior to editing, proofing, and formal publicationof the final Version of Record (VoR). This work is currently citable byusing the Digital Object Identifier (DOI) given below. The VoR will bepublished online in Early View as soon as possible and may be differentto this Accepted Article as a result of editing. Readers should obtainthe VoR from the journal website shown below when it is publishedto ensure accuracy of information. The authors are responsible for thecontent of this Accepted Article.

To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201705123Angew. Chem. 10.1002/ange.201705123

Link to VoR: http://dx.doi.org/10.1002/anie.201705123http://dx.doi.org/10.1002/ange.201705123

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Self-assembled Oligopeptide as a Versatile NMR Alignment

Medium for the Measurements of Residual Dipolar Couplings in

Methanol

Xinxiang Lei*, Feng Qiu, Han Sun, Liwen Bai, Wen-Xuan Wang, Wensheng Xiang and Hongping Xiao

Residual dipolar coupling (RDC) constitutes a powerful structural

parameter for the determination of constitution, conformation and

configuration of organic molecules. Here, we report the first liquid

crystalline based orientating medium that is compatible with MeOH,

thus enabling RDC acquisitions of a wide range of intermediate to

polar organic molecules. The liquid crystals were produced by the

self-assembled oligopeptide nanotubes (AAKLVFF), which are

stable at very low concentration. The presented alignment medium

is highly homogeneous and the size of RDCs can be scaled with the

concentration of the peptide. To assess the accuracy of the RDC

measurement by employing this newly introduced medium, seven

bioactive natural products from different classes were chosen and

analyzed. The straightforward preparation of the anisotropic

alignment sample will offer a versatile and robust protocol for the

routine RDC measurement of natural products.

Residual dipolar coupling (RDC) is a highly valuable structural

parameter for biomacromolecules[1] as well as small organic

molecules[2] with respect to constitution, conformation,

configuration and structural dynamics. The application of RDC

for organic compounds has been significantly accelerated owing

to the recent progresses on the development of new pulse

sequences, alignment media and analysis methods.[3]

A prerequisite for RDC measurement is the availability of

suitable alignment media for introducing the necessary

anisotropy to the analytes. Two main classes of alignment media

have been introduced to organic molecules, which are stretched

polymer gels and lyotropic liquid crystalline (LLC) phases.[3e-h]

Polymer gels have been widely applied for acquiring anisotropic

NMR data, as various polymer based media have been

developed for different organic solvents.[4] Notably, Luy et.al

proposed a robust cross-linked poly(ethylene oxide) (PEO) gel,

which is until now the only orienting medium that covers a wide

range of solvent compatibility.[5] LLCs are another good option to

align small molecules because of their excellent NMR

spectroscopic properties and their ability to simultaneously align

organic molecules. However, most of the LC phases e.g.

PBLG,[2c] polyguanidines,[6] polyisocyanates,[7] polyacetylenes,[8]

polyisocyanopeptides[9] are only compatible with aploar solvents

such as chloroform or a mixture of CDCl3 with polar solvents[10],

while a few phases such as ACHC-rich β-peptides[11] and

disodium cromoglycate[12] are compatible with water. In our

previous work, we proposed a series of graphene oxide based

LLCs as orienting media for polar solvents such as

dimethylsulfoxide (DMSO)[13]. Nevertheless, to best of our

knowledge, until now there is still no LC phase that is compatible

with methanol (MeOH), which is a very frequently used solvent

in natural product chemistry, as it is compatible with a wide

range of molecule classes including alcohol, carboxylic acid,

amine and ester. Our aim was therefore to develop a new

methanol compatible LLC phase, which is stable at sufficiently

low critical concentrations and simultaneously can be produced

easily in large scale.

Recently, self-assembled oligopeptides have attracted

immense attention due to their potential applications in

biomedicine, biomimetic materials and nanotechnology.[14]

Various hierarchical architectures including nanofibrils,

nanotubes, nanowires using peptide building blocks have been

developed in the last few years.[14] Inspired by filamentous Pf1

bacteriophage[15] and DNA-nanotube[16] as excellent orientational

ordering media in aqueous solution, we started our

investigations on self-assembled peptides that are soluble in

organic solvents. In fact, several oligopeptide based anticancer

drugs such as nafarelin, detirelix, and leuprolide, have been

shown to form lyotropic liquid crystalline phases with β-sheet

rod-like architecture.[17] More interestingly, Hamley and co-

workers developed a peptide nanotube, which can form a

nematic phase at 1 wt % concentration in methanol.[18] This self-

assembled oligopeptide has the sequence of AAKLVFF, which

was derived from a fragment of the amyloid β-peptide Aβ-(16-

20), KLVFF, whose structure and properties have been

systematically investigated. Furthermore, the self-assembly

mechanism and the formation of nematic phase in methanol of

AAKLVFF has been comprehensively studied. Last but not least,

synthesis of this natural amino acids derived short peptide is

straightforward and the peptide can be produced in large scale.

All of these aspects indicate that AAKLVFF peptide could be an

ideal alignment medium for MeOH solvent.

We observed a birefringent texture of 40 mg/mL AAKLVFF

peptide in methanol using polarized optical microscopy (Figure

S1), which is in accordance with previous studies revealing the

formation of a nematic phase of the peptide at sufficient high

concentration [19]. To further monitor the completeness of the

phase transition and evaluate the anisotropic properties of

AAKLVFF peptide as an alignment medium, 2H NMR spectra of

the medium with different peptide concentration were recorded.

The quadrupole splitting of deuterated MeOH signals

augmented while the concentration of the peptide was

increased, indicating that the strength of the alignment can be

tuned through adjustment of the medium concentration (Fig. S2).

At a concentration of 40 mg/mL, quadrupolar couplings of 18.3

Hz and 2.8 Hz were observed for OD and CD3, respectively. The

doublet 2H NMR signals are sharp and highly symmetric, with a

[∗ ] Prof. Dr. X. Lei, F. Qiu, L. Bai, W.X. Wang

School of Pharmaceutical Sciences, South Central University for

Nationalities, Wuhan, 430074, P. R. China

E-mail: [email protected]

Dr. H.Sun,

Leibniz-Institut fur Molekulare Pharmakologie (FMP), Robert-

Roessle-Strasse 10, 13125 Berlin, Germany

Prof.W. Xiang

School of Life Science, Northeast Agricultural University, Harbin,

Heilongjiang Province 150030, China

Prof.H.Xiao

College of Chemistry & Materials Engineering, Wenzhou University,

Wenzhou 325035, P. R. China

Supporting information for this article is given via a link at the end of

the document.

10.1002/anie.201705123Angewandte Chemie International Edition

This article is protected by copyright. All rights reserved.

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line width of 4.1 Hz for OD and 1.2 Hz for CD3 signals,

respectively (Fig S3). This result suggested that the alignment

media prepared with AAKLVFF nanotubes are highly

homogenous with low viscosity, which allows us to shim the

NMR samples as easy as with isotropic solution.

Scheme 1. Molecular structures of the peptide AAKLVFF and a series of

analytes for NMR measurement.

Figure 1. (a) A photograph of AAKLVFF powder in a NMR tube and a solution

of it with MeOH. (b) 2H NMR spectrum (92.1 MHz) of the anisotropic sample

(40 mg/mL peptide LC phase in MeOH), a 2H quadrupolar splitting of 18.30 Hz

of OD was observed.

To show the compatibility and applicability of the AAKLVFF

nanotube as an applicable alignment medium for the acquisition

of high quality RDC data, we selected a series of natural

products with different polarities, functionalities, and structural

complexities. The structural formula of the test compounds 1-7

are shown in Scheme 1. Artemether 1 is a drug used for the

treatment of malaria diseases and it is a derivative of

artemisinin, the discovery of which was awarded for Nobel prize

in 2015. Dihydroartemisinin has been employed as a test

compound for the RDC measurements and analysis in our

previous study.[13b] Gibberellin 2 is a diterpenoid acid and serve

as a hormone that regulates growth and influences various

developmental processes in plants. Ingenol 3 is a natural

product that belongs to the class of diterpene. Its derivative

ingenol mebutate is an approved drug for the tropical treatment

of actinic keratosis. Ginkgolide B 4 is a biologically active

terpenic lactone with six fused five-membered rings.

Actinomycin D 5 is a polypeptide antibiotic that currently used in

the chemotherapy medication for a number of types of cancers.

Furthermore, we selected two small aromatic compounds, which

are indole-3-acetic acid 6 and aristolochic acid A 7 for testing the

compatibility of AAKLVFF peptide with aromatic compounds.

To align the test compounds we used a concentration of 6-

40.0 mg/mL AAKLVFF nanotube, leading to aquadrupolar

coupling of 2.8-21.5 Hz for OD signal. One-bonded proton

carbon couplings of all test compounds were acquired with F2 1H-coupled CLIP-HSQC experiment.[20] RDC values were

directly extracted from the difference between the couplings

measured in isotropic and aligned samples. A portion of the

overlaid CLIP-HSQC spectra of artemether 1 in both conditions

is depicted in Figure S5, showing the well resolved signals under

the aligned condition. It should be noted that the background

signals of AAKLVFF could be observed (Figure S25-26),

although after self-assembling the signal of the monomer was

reduced by 80%. Nevertheless, we did not notice significant

disturbances of them to the solute signals as they are well

separated in the two-dimensional NMR spectra and have sharp

lines. Once the oligopeptide is self-assembled (about 3 days),

the intensity of the background signal does not increase over

time. To further investigate the influence of the background

signals on the signals of analytes, we aligned 5 mg of

polypeptide based natural product actinomycin D (molecular

weight: 1255 gmol-1) in 10 mg/mL AAKLVFF LLC with a

quadrupolar deuterium splitting of 5.7 Hz for OD signal.

Altogether we could measure 26 sets of 1DCH in a range of -17.8

to 9.8 Hz without any overlap between the signals of

actinomycin D and the self-assembled peptide (Fig. 2).

Figure 2. A section of the 600 MHz 1H,13C-CLIP-HSQC spectra of 8 mmol/L

actinomycin D in the isotropic phase (blue contours) and in 10 mg/mL peptide

LCs (anisotropic, red contours).

Taking into account that non-covalent interactions such as

hydrogen bonding, π-π and van-der-Waals interactions are the

driving forces for self-assembly of the peptides, we chose IAA as

a sample compound to investigate its compatibility with the

AAKLVFF nanotube, as IAA contains simultaneously an

aromatic ring, a hydrogen bonding acceptor and donor. We

added 16 mg/mL of the IAA sample into 40 mg/mL of AAKLVFF

nanotube medium. No precipitations or aggregates were

observed. Furthermore, a series of CLIP-HSQC spectra of IAA

were recorded at different concentrations of AAKLVFF (Fig. 3),

revealing that the alignment strength is scaled with the

concentration of the media. Notably, IAA could be aligned at a

LLC concentration of as low as 6 mg/mL, which allows us to



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extract a series of RDCs ranging from -1.8 to 13.9 Hz.

Compared to other established LLC phases, AAKLVFF LLC has

a remarkably low critical concentration. The high scalability of

the AAKLVFF phase makes it a versatile and tunable alignment

medium with broad applicability for small organic molecules.

Figure 3. CLIP-HSQC spectra of IAA at various concentrations of peptides

anisotropic phases.

In addition, our newly introduced alignment medium is stable

at a wide range of temperatures (273-333K) with increasing

alignment strength with decreasing temperature (Figure S22).

Furthermore, we noted that the alignment medium shows an

optimal homogeneity close or below pH 7. Above pH 8, although

the birefringent texture ofthe medium could still be observed, the

viscosity of the medium was increased significantly (Figure S1

and S24).

We further investigate the compatibility of AAKLVFF nanotube

with solvent mixtures such as MeOH/acetone and MeOH/DMSO.

The LLC phase of AAKLVFF nanotube was stable at a maximum

concentration ratio of 40% for acetone and 30% for DMSO,

respectively (Figure S13 and S15). Above the maximum

concentration, self-assembled oligopeptide will be partially

dissolved in the solvent. The RDC measurements of gingkgolide

B and aristolochic acid A were conducted in MeOH/acetone and

MeOH/DMSO solvent mixtures, respectively. Notably, only 1 mg

of the aristolochic acid A sample was used for the RDC

measurement. Furthermore, the analytes can be easily separated

from the AAKLVFF LLC phase by routine column

chromatography, which is a highly important feature for the RDC

measurements of novel natural products with limited availability.

To demonstrate the applicability of AAKLVFF LLC in the RDC-

enhanced structural elucidation of organic molecules, we

validated the structure of five natural products 1-5. IAA 6 and

aristolochic acid 7 are two compounds with planar structure, for

which the alignment tensor cannot be easily determined using the

algorithms implemented in the conventional software packages.

For the RDC fitting, we employed the DFT optimized structures at

B3PW91-D3/pcSeg-1level using X-ray structures of 1,2and 4 as

references[21]. As no X-ray structure was available for ingenol 3,

we modified the X-ray structure of 20-deoxyingenol[22]and further

optimized it with DFT. For actinomycin D 4, a bound conformation

of it with deoxyguanosine was employed in the RDC analysis[23].

We calculated the alignment tensor of each structure using the

singular value decomposition method (SVD)[24] as implemented in

the program package MSpin (http://www.mestrelabs.com)[25].

Theoretically predicted RDCs were determined from the

computed alignment tensor and further compared with the

experimentally calculated ones. The quality factors (Q factors)

between experimental and predicted RDCs for all test compounds

1-5 are close or below 0.2. Artemether, gibberelin and ginkgolide

B are highly rigid molecules with multiple fused rings. All

molecules show excellent fitting between experimental and back-

calculated RDCs with Q factors lower than 0.1 (Table 1). Ingenol

contains partial flexibility in the ring systems, whereas

actinomycin D 4 is potentially flexible with several rotatable

bonds. Considerably low Q factors for both molecules (Q=0.18 for

ingenol and Q=0.20 for actinomycin D) suggested that the X-ray

structure of ingenol and bound conformation of actinomycin D are

the major conformations in solution.

Table 1. A summary of molecule classes, number of experimental RDCs and Q

factor for each test compound.

Compound Numbers

of RDCs

Q factor Condition

number of

SVD

Artemether 11 0.06 16.0

Gibberelin 13 0.04 3.2

Ingenol 12 0.18 4.0

Gingkgolide B 8 0.08 7.2

actinomycin D 26 0.20 5.5

In summary, we presented a liquid crystal forming AAKLVFF

peptide as a versatile alignment medium in organic solvents. This

work is the first example of a MeOH based lyotropic liquid

crystalline as an aligning medium at low critical concentration.

The medium shows high scalability for the precise and accurate

acquisition of RDCs. Seven natural products containing very

different functional groups were measured to demonstrate the

wide compatibility and applicability for the RDC analysis of natural

products. Moreover, the LC phase is highly stable at a wide range

of concentration and temperature, which allow us to precisely

measure molecules with different sizes by varying the degree of

alignment. Furthermore, the synthesis is easy and the medium

can be produced in large scale. We believe the introduced

medium will complement the existing media and enable the RDC

measurements of organic molecules as a routine tool.

Acknowledgements

This work was supported by the National Natural Science

Foundation of China (21572164); Key Projects of Technological

Innovation of Hubei Province (No. 2016ACA138). HS and XXL

thank the Sino-German Center for Research Promotion

(GZ1289). The authors thank the Analytical & Measuring Center,

School of Pharmaceutical Sciences, SCUN for their help with

NMR measurements.



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Keywords: residual dipolar coupling•alignment medium •liquid

crystals•self-assembled peptide•NMR spectroscopy

[1] (a) N. Tjandra, A. Bax, Science 1997, 278, 1111–1114. (b), J. R.Tolman,

K. Ruan,Chem. Rev. 2006, 106, 1720-1736.(c) J. H. Prestegard, C. M.

Bougault, A. I. Kishore, Chem. Rev. 2004, 104, 3519-3540.

[2] (a) A. Mangoni, V. Esposito, A. Randazzo, Chem. Commun. 2003, 154–

155. (b) J. Yan, A. D. Kline, H. Mo, M. J. Shapiro, E. R. Zartler, J. Org.

Chem. 2003, 68, 1786–1795. (c) C. M. Thiele, S. Berger, Org. Lett.

2003, 5, 705-708. (d) L. Verdier, P. Sakhaii, M. Zweckstetter, C.

Griesinger, J. Magn. Reson. 2003, 163, 353-359. (e) C. Aroulanda, V.

Boucard, F. Guibѐ, J. Courtieu, D. Merlet, Chem. Eur. J. 2003, 9, 4536-

4539.

[3] (a) W. Waratchareeyakul, E.Hellemann, R. R. Gil, K. Chantrapromma, M.

K. Langat, D. A. Mulholland,J. Nat. Prod. 2017, 80, 391–402. (b) E.

Mevers, J. Saurí, Y. Liu, A. Moser, T. R. Ramadhar, M. Varlan, R. T.

Williamso, G. E. Martin, J. Clardy, J. Am. Chem. Soc. 2016, 138,

12324–12327. (c) L.Y. Liu, H. Sun, C. Griesinger, J. K. Liu, Nat. Prod.

Bioprospect. 2016, 6, 41-48. (d) N. Marcó, A. A. Souza, P.Nolis, C.

Cobas, R. R. Gil, T. Parella, J. Org. Chem. 2017, 82, 2040–2044. (e) V.

Schmidts, Magn. Reson. Chem. 2017, 55, 54–60. (f) R. R. Gil, C.

Griesinger, A. Navarro–Vázquez, H. Sun, Structure Elucidation in

Organic Chemistry, Wiley–VCH Verlag GmbH & Co, KGaA, 2015, pp.

279–324. (g) C. M. Thiele, Eur. J. Org. Chem. 2008, 5673–5685. (h) G.

Kummerlöwe, B.Luy,TrAC 2009, 28, 483–493. (i) E. Troche-Pesqueira;

C. Anklin, R. R. Gil, A. Navarro-Vázquez, Angew. Chem., Int. Ed. 2017,

56, 3660-3664; Angew. Chem.2017, 129, 3714-3718. (j) Y. Liu, J.

Saurí, E. Mevers, M. W. Peczuh, H. Hiesmdtra, J. Clardy, G. E. Martin,

R. T. Williamson, Science 2017, 356, DOI: 10.1126/science.amm5349.

[4] (a)Y. E. Moskalenko, V. Bagutski, C. M. Thiele, Chem. Commun. 2017, 53,

95-98. (b) M. E. García, S. R. Woodruff, E. Hellemann, N. V.Tsarevsky,

R. R. Gil, Magn. Reson. Chem. 2017, 55, 206–209. (c) L. F. Gil-Silva,

R. Santamaría-Fernandez, A. Navarro-Vázquez, R. R. Gil, Chem. -

Eur. J. 2016, 22, 472−476. (d) C. Gayathri, N. V. Tsarevsky, R. R. Gil,

Chem. Eur. J. 2010, 16, 3622-3626. (d) R. R. Gil, C. Gayathri, N. V.

Tsarevsky, K. Matyjaszewski, J. Org. Chem. 2008, 73, 840−848. (e) J.

C. Freudenberger, P. Spiteller, R. Bauer, H. Kessler, B. Luy, J. Am.

Chem. Soc. 2004, 126, 14690–14691. (f) P. Haberz, J. Farjon, C.

Griesinger, Angew. Chem., Int. Ed. 2005, 44, 427–429; Angew. Chem.

2005, 117, 431–433. (g) G. Kummerlöwe, J. Auernheimer, A. Lendlein,

B. Luy, J. Am. Chem. Soc. 2007, 129, 6080–6081.

[5] C. Merle, G. Kummerlöwe, J. C. Freudenberger, F. Halbach, W. Stower, C.

L. vonGostomski, J. Hopfner, T. Beskers, M. Wilhelm, B. Luy, Angew.

Chem. Int. Ed. 2013, 52, 10309–10312; Angew. Chem. 2013, 125,

10499 –10502.

[6] L. Arnold, A. Marx, C. M. Thiele, M. Reggelin, Chem. Eur. J. 2010, 16,

10342-10346.

[7] M. Dama, S. Berge, Org. Lett. 2012, 14, 241–243.

[8] N. C. Meyer, A. Krupp, V. Schmidts, C. M. Thiele, M. Reggelin, Angew.

Chem. Int. Ed. 2012, 51, 8334–8338; Angew. Chem. 2012,124, 8459–

8463.

[9] G. W. Li, J. M. Cao, W. Zong, L. Hu, M. L. Hu, X. X. Lei, H. Sun, R. X. Tan,

Chem. Eur. J. 2017, 23, 7653-7656.

[10] (a) R. W. Duke, W. A. D. B. Du Pre. Hines, E. T. Samulski, J. Am. Chem.

Soc.1976, 98, 3094-3101. (b) A. Marx, B. Böttcher, C. M. Thiele, Chem.

Eur. J. 2010, 16, 1656–1663.

[11] C. M. Thiele, W. C. Pomerantz, N. L. Abbott, S. H. Gellman, Chem.

Commun. 2011, 47, 502–504.

[12] E. Troche-Pesqueira, M. M. Cid, A. Navarro-Vázquez, Org. Biomol.

Chem. 2014, 12, 1957–1965.

[13] (a) X. X. Lei, Z. Xu, H. Sun, S. Wang, C. Griesinger, L. Peng, C. Gao, R.

X. Tan. J. Am. Chem. Soc. 2014, 136,11280-11283.(b) W. Zong, G. W.

Li, J. M. Cao, X. X. Lei, M. L.Hu, H. Sun, Griesinger, C.; Tan, R. X.

Angew. Chem., Int. Ed. 2016, 55, 3690-3693; Angew. Chem. 2016,

128, 3754–3757.

[14] (a) L. Adler-Abramovich, E. Gazit, Chem. Soc. Rev. 2014, 43, 6881-6893.

(b) S. Zhang, Acc. Chem. Res. 2012, 45, 2142-2150.

[15] L. Liu, K. Busuttil, S. Zhang, Y. Yang, C. Wang, F. Besenbacher, M.

Dong, Phys. Chem. Chem. Phys. 2011, 13, 17435–17444.

[16] M. R. Hansen, L. Meuller, A. Pardi, Nat. Struct. Biol. 1999, 5, 1065-1074.

[17] (a) S. M.Douglas, J. J.Chou, W. M. Shih, Proc. Natl. Acad. Sci. U.S. A.

2007, 104, 6644−6648. (b) J. Lorieau, L. Yao, A. Bax, J. Am. Chem.

Soc. 2008, 130, 7536−7537.

[18] (a) M. F. Powell, L. M. Sanders, A. Rogerson, V. Si, Pharm. Res. 1991, 8,

1258-1263. (b) M. M. Tan, C. A. Corley, L. L. Stevenson, Pharm. Res.

1998, 15, 1442-1448.

[19] M. J. Krysmann, V. Castelletto, J. E.McKendrick, L. A.Clifton, I. W.

Hamley, P. J. F. Harris, S. M. King, Langmuir 2008, 24, 8158–8162.

[20] A. Enthart, J. C. Freudenberger, J. Furrer, H. Kessler, B. Luy, J. Magn.

Reson. 2008, 192, 314–322.

[21] (a) L. W. Chen, C. Z. Wang, Q. W. Wu, Chin. Pharm.2000, 31, 450-452.

(b) L. Kutschabsky, G. J. Adam, Chem. Soc. Perkin Trans. 1 1983,

1653-1655. (c) L. Dupont, O. Dideberg, G. Germain, P. Braquet, Acta

Crystallogr. Sect. C: Cryst. Struct. Commun.1986, 42, 1759.

[22] A. Nickel, T. Maruyama, H. Tang, P. D. Murphy, B. Greene, N. Yusuff, J.

L. Wood, J. Am. Chem. Soc. 2004, 126, 16300-16301.

[23] S. C.Jain, H. M.Sobell, J. Mol. Biol. 1972, 68, 1-10.

[24] J.A. Losonczi, M. Andrec, M.W.F. Fischer, J.H. Prestegard, J. Magn.

Reson.1999, 138, 334–342.

[25] A.Navarro-Vázquez, Magn. Reson.Chem. 2012, 50, S73–S79.



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Layout 1:

COMMUNICATION Alignment medium: A novel, robust, versatile anisotropic medium from self-assembled peptide for the measurement of residual dipolar coupling in MeOH, which are stable at very low concentration. The presented alignment medium is highly homogeneous and the size of RDCs can be scaled with the concentration of the peptide.

Xinxiang Lei*, FengQiu, Han Sun, Liwen

Bai, Wen-Xuan Wang, Wensheng Xiang

and Hongping Xiao

Page No. – Page No.

Self-assembled Oligopeptide as a

Versatile NMR Alignment Medium for

the Measurements of Residual

Dipolar Couplings in Methanol

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