Related Experiment Video
Updated: Feb 2, 2026
14:55
Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
16.0K
pH-dependent thermodynamic intermediates of pHLIP membrane insertion determined by solid-state NMR spectroscopy
Sarah A Otieno1, Samuel Z Hanz1, Bianca Chakravorty1
1Department of Chemistry, Binghamton University, The State University of New York, Binghamton, NY 13902.
Summary
The pH low insertion peptide (pHLIP) undergoes multistage insertion into membranes, not just two states. This discovery reveals intermediate pH states crucial for understanding pHLIP
Area of Science:
- Biophysics
- Membrane Protein Dynamics
- Biochemistry
Background:
- The pH low insertion peptide (pHLIP) is vital for cancer diagnosis and drug delivery.
- pHLIP's transition from a coil to a transmembrane helix is pH-dependent.
- Understanding intermediate pH states is key for pHLIP applications.
Purpose of the Study:
- To investigate pHLIP's behavior at intermediate pH values (6.4, 6.1, 5.8).
- To elucidate the sequential protonation events during pHLIP membrane insertion.
- To establish a detailed model of pHLIP-membrane interactions.
Main Methods:
- Advanced solid-state NMR spectroscopy.
- Utilized palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC) unilamellar vesicles.
- Examined pHLIP interactions across a pH range (7.4 to 5.3).
Main Results:
- Discovered distinct thermodynamic intermediate states at intervening pH values.
- Identified sequential protonation of D/E residues during insertion.
- Demonstrated that pHLIP insertion is a multistage process.
Conclusions:
- pHLIP insertion is a complex, multistage process involving sequential D/E residue titrations.
- The findings support a refined model of pHLIP-membrane interactions.
- This multistage model has significant implications for pHLIP-based technologies.
Keywords:
intermediate stateslipid dynamicsmembrane insertionpH low insertion peptidesolid-state nuclear magnetic resonance spectroscopyMore Related Videos
Related Concept Videos
02:38Third Law of Thermodynamics
22.1K
A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero.
22.1K
02:49Second Law of Thermodynamics
27.1K
In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
27.1K
01:19NMR Spectroscopy Of Amines
11.1K
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is...
11.1K
01:14NMR Spectroscopy of Aromatic Compounds
6.3K
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range.
6.3K
01:34NMR Spectroscopy of Benzene Derivatives
11.2K
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling...
11.2K
01:15NMR Spectroscopy: Chemical Shift Overview
3.3K
The position of the absorption signal of a sample is reported relative to the position of the signal of tetramethylsilane (TMS), which is added as an internal reference while recording spectra. The difference between the absorption frequencies of the sample and TMS (in Hz) is divided by the spectrometer operating frequency (in MHz) to obtain a dimensionless quantity called the chemical shift. It is reported on the δ (delta) scale and expressed in parts per million.
For instance, the proton...
For instance, the proton...
3.3K