How Tetrahedral Are Methyl Groups in Proteins? A Liquid Crystal NMR Study
نویسنده
چکیده
A small degree of protein alignment with an external magnetic field can be obtained in a dilute aqueous liquid crystalline solution of dimyristoylphosphatidylcholine (DMPC) and dihexanoylphosphatidylcholine (DHPC). It is demonstrated that residual one-bond 13C-13C and 13C-1H dipolar couplings of methyl groups in weakly aligned human ubiquitin can be measured with high accuracy. Experimentally, the ratio between 13C-1H and 13C-13C dipolar couplings is found to be -3.17 ( 0.03. Assuming a static conformation of the methyl group, rapidly spinning about its 3-fold symmetry axis, this ratio corresponds to an average C-C-H bond angle of 110.9 ( 1°, which is larger than the ideal tetrahedral value of 109.5°. Data indicate that the geometry of the various methyl groups is quite uniform, but that small (e1°) deviations between the C-C vector and the axis connecting the methyl carbon to the geometric center of the three methyl protons may occur. The largest outlier is found for Ala46, which has a positive φ backbone angle, causing its methyl group to be within van der Waals contact of the preceding carbonyl oxygen.
منابع مشابه
Multiple quantum NMR study of correlation of two methyl groups
Molecules which have rotating groups may show coupled motions. As an example, two adjacent methyl groups may exhibit some degree of correlated motion as two wheels in gear. 1 The spectra obtained by traditional single quantum NMR in oriented molecules may sometimes be complicated and difficult to analyze. However, the techniques of multiple quantum (MQ) NMR spectroscopy can yield analyzable spe...
متن کاملP-30: Developmental Capacity and Blastocyst Formation of Thawed Tetrahedral Versus Non-Tetrahedral 4-cell Stage Mouse Embryos After Vitrification
Background: It was reported in a literature that approximately one third of the 4-cell stage embryos did not exhibit a tetrahedral shape. Non-tetrahedral embryos showed a lower in vitro developmental potential than tetrahedral embryos. Recently vitrification technology has been widely employed for embryo cryopreservation. The objective of this study was to prove our hypothesis that vitrified - ...
متن کاملMolecules with large-amplitude torsional motion partially oriented in a nematic liquid crystal: ethane and isotopomers.
An NMR study on ethane and five isotopomers dissolved in the nematic liquid crystal Merck ZLI 1132 is performed. A consistent set of dipolar and quadrupolar couplings is obtained. The dipolar couplings are corrected for harmonic vibrational effects, while the contribution from the torsional motion is incorporated classically. The corrected dipolar couplings cannot be understood in terms of a re...
متن کاملuid–liquid transition in a tetrahedral fluid
For a model known to exhibit liquid–liquid transitions, we examine how varying the bond orientational flexibility affects the stability of the liquid–liquid transition relative to that of the crystal phases. For very rigidly oriented bonds, the crystal is favored over all amorphous phase transitions. We find that increasing the bond flexibility decreases both the critical temperature Tc for liq...
متن کاملLiquid-phase characterization of molecular interactions in polyunsaturated and n-fatty acid methyl esters by 1H low-field nuclear magnetic resonance
BACKGROUND To identify and develop the best renewable and low carbon footprint biodiesel substitutes for petroleum diesel, the properties of different biodiesel candidates should be studied and characterized with respect to molecular structures versus biodiesel liquid property relationships. In our previous paper, (1)H low-field nuclear magnetic resonance (LF-NMR) relaxometry was investigated a...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 1999