Recent studies have identified a predictable movement pattern of the common carotid artery wall in the longitudinal direction. While there is evidence that the magnitude of this carotid artery longitudinal wall motion (CALM) is sensitive to cardiovascular health status, little is known about the determinants of CALM. The purpose of this integrative study was to evaluate the contribution of left ventricular (LV) cardiac motion and local blood velocity to CALM. Simultaneous ultrasound measurements of CALM, common carotid artery mean blood velocity (MBV), and left ventricular motion were performed in ten young, healthy individuals (6 males; 22 ± 1 years). Peak anterograde CALM occurred at a similar time as peak MBV (18.57 ± 3.98% vs. 18.53 ± 2.81% cardiac cycle; t‐test: P = 0.94; ICC: 0.79, P < 0.01). The timing of maximum retrograde CALM displacement was different, but related, to both peak apical (41.00 ± 7.81% vs. 35.33 ± 5.79% cardiac cycle; t‐test: P < 0.01; ICC: 0.79, P < 0.01) and basal rotation (41.80 ± 6.12% vs. 37.30 ± 5.66% cardiac cycle; t‐test: P < 0.01; ICC: 0.74, P < 0.01) with peak cardiac displacements preceding peak CALM displacements in both cases. The association between basal rotation and retrograde CALM was further supported by strong correlations between their peak magnitudes (r = −0.70, P = 0.02), whereas the magnitude of septal longitudinal displacement was not associated with peak CALM (r = 0.11, P = 0.77). These results suggest that the rotational mechanical movement of the LV base may be closely associated with longitudinal mechanics in the carotid artery. This finding may have important implications for interpreting the complex relationship between ventricular and vascular function.

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Longitudinal motion of the intima-media and adventitia layers of the common carotid artery (CCA) wall were assessed with ultrasound speckle tracking in seven individuals with spinal cord injury (SCI), who are considered at increased risk of cardiovascular disease, and in seven able-bodied participants. CCA longitudinal wall displacement and intramural shear strain were compared to traditional markers of arterial health, including CCA stiffness and intima-media thickness (IMT). For each cardiac cycle, longitudinal CCA wall motion was characterized by bidirectional movement patterns containing motion retrograde to blood flow during systole, followed by antegrade motion during diastole. Relative displacement of the intima-media versus the adventitia was used to calculate longitudinal intramural shear strain and provided insight to local arterial wall properties. The retrograde intramural shear strain was smaller in individuals with SCI by 60·2% (P<0·05) compared to able-bodied participants, showing smaller peak displacements in both the intima-media (P<0·05) and adventitia (P<0·05). In the antegrade direction, there were no group differences in either longitudinal displacements or shear strain. The group differences observed in the retrograde wall motion phase were greater than those observed for CCA stiffness or IMT and were found to be independent of both indices, indicating indices of the retrograde phase intramural shear strain may be a novel and sensitive marker of vascular health. Our findings demonstrate that assessment of longitudinal arterial wall shear strain may provide valuable insight into vascular structure and function and may hold potential for the early detection of cardiovascular disease.

We have investigated the lysine side chain amines in the 34 kDa catalytic domain from Cellulomonas fimi beta-(1,4)-glycosidase Cex (or CfXyn10A) using 1H-detected 15N heteronuclear correlation NMR spectroscopy. Signals from the 1Hzeta ( approximately 8 ppm) and 15Nzeta ( approximately 35 ppm) of Lys302 in the unmodified enzyme and Lys47 in a trapped cellobiosyl-enzyme intermediate were detected in a 1H-15N HMQC spectrum (pH 6.5 and 30 degrees C). The amine of Lys302 forms a buried ion pair, and that of Lys47 is hydrogen bonded to the cellobioside. Both lysines are positively charged, as unambiguously demonstrated by the splitting of their 15Nzeta signals into quartets (|1JNH| approximately 75 Hz) in a 1H-15N HSQC spectrum recorded without 1H decoupling during 15N evolution. Qualitative insights into the dynamic properties of these lysines are also provided by the deviations of their quartet intensity ratios from that of approximately 3:1:1:3 expected for a highly mobile amine. On the basis of the observed ratios of approximately 1:1:1:1 for the quartet of Lys302 and approximately 0.5:1:1:0.5 for Lys47, the amine of the latter active site residue is most rigidly positioned. Signals from at least 8 and 10 additional positively charged, mobile amines in Cex were observed at 10 degrees C and pH 6.5 and 5.6, respectively. By using conditions of reduced temperature, slightly acidic pH, and low general base concentrations, as well as water flipback pulses to minimize the effects of hydrogen exchange, 1H-15N correlation experiments provide a sensitive route to directly investigate the charge states and dynamic properties of the N-terminal and side chain amines in proteins and protein complexes.