Host-guest complexes between cryptophane-A as host and dichloromethane and chloroform as guests are investigated using (1)H and (13)C NMR spectroscopy. Moreover, a related cryptophane, with the methoxy groups replaced by butoxy units (cryptophane-But), and its complexes with the same guests were also studied. Variable temperature spectra showed effects of chemical exchange between the free and bound guests, as well as of conformational exchange of the host. The guest exchange was studied quantitatively by exchange spectroscopy or line shape analysis. Extraction of kinetic and thermodynamic parameters led to the characterization of the affinity between guests and hosts. On the other hand, the host exchange was investigated by means of (13)C Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion which aims at the determination of the transverse relaxation rate R2, the inverse of the transverse relaxation time T2, as a function of the repetition of the π pulses in a CPMG train. The variation of the measured transverse relaxation rate with the repetition rate νCPMG indicated conformational exchange occurring on the microsecond-millisecond time scale. Structural information was obtained through measurements of cross-relaxation rates, both within the host and between the host and the guest protons. The NMR results were supported by DFT calculations.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3963437 | PMC |
| http://dx.doi.org/10.1021/jp4105272 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Tendon evaluation with ultrashort Echo Time (UTE) MRI: A Systematic Review.
Front Musculoskelet Disord
March 2024
Department of Radiology, University of California, San Diego, San Diego, CA, United States.
Tendon disease ranks among the leading reasons patients consult their general practitioners, comprising approximately one-third of musculoskeletal appointments. Magnetic resonance imaging (MRI) is regarded as the gold standard for assessing tendons. Due to their short transverse relaxation time (T2), Tendons show up as a signal void in conventional MRI scans, which employ sequences with echo times (TEs) around several milliseconds.
View Article and Find Full Text PDFTwo synergistic types of muscles were detected during forearm rotation exercise by T cumulative frequency curves using 0.2 T magnetic resonance imaging.
J Physiol Sci
January 2025
Department of Rehabilitation, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, 321-0293, Tochigi, Japan. Electronic address:
The purpose of this study was the detection and characterization of synergistic muscle activity. Using T-map MRI, T values for 10 forearm muscles in 11 healthy adult volunteers were obtained in the resting state and after isotonic forearm supination and pronation exercises with the elbow extended. T was normalized by Z = (T-T)/SD, where T was T after exercise, while T and SD were the reference values of 34 ms and 3 ms, respectively.
View Article and Find Full Text PDFPoor self-reported sleep is associated with prolonged white matter T2 relaxation in psychotic disorders.
Front Psychiatry
January 2025
Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, United States.
Background: Psychotic disorders are characterized by white matter (WM) abnormalities; however, their relationship with the various aspects of illness presentation remains unclear. Sleep disturbances are common in psychosis, and emerging evidence suggests that sleep plays a critical role in WM physiology. Therefore, it is plausible that sleep disturbances are associated with impaired WM integrity in these disorders.
View Article and Find Full Text PDFBrain tumor enhancement prediction from pre-contrast conventional weighted images using synthetic multiparametric mapping and generative artificial intelligence.
Quant Imaging Med Surg
January 2025
Radiology and Nuclear Medicine Department, Erasmus MC, Rotterdam, The Netherlands.
Background: Gadolinium-based contrast agents (GBCAs) are usually employed for glioma diagnosis. However, GBCAs raise safety concerns, lead to patient discomfort and increase costs. Parametric maps offer a potential solution by enabling quantification of subtle tissue changes without GBCAs, but they are not commonly used in clinical practice due to the need for specifically targeted sequences.
View Article and Find Full Text PDFχ-sepnet: Deep Neural Network for Magnetic Susceptibility Source Separation.
Hum Brain Mapp
February 2025
Laboratory for Imaging Science and Technology, Department of Electrical and Computer Engineering, Seoul National University, Seoul, Republic of Korea.
Magnetic susceptibility source separation (χ-separation), an advanced quantitative susceptibility mapping (QSM) method, enables the separate estimation of paramagnetic and diamagnetic susceptibility source distributions in the brain. Similar to QSM, it requires solving the ill-conditioned problem of dipole inversion, suffering from so-called streaking artifacts. Additionally, the method utilizes reversible transverse relaxation ( ) to complement frequency shift information for estimating susceptibility source concentrations, requiring time-consuming data acquisition for (e.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!