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K Long

Publications and source records attributed to K Long.

At least 37 records · Page 2Linked to original sources
PubMed1994

Structure-function relationships in the 47-kDa antenna protein and its complex with the photosystem II reaction center core: insights from picosecond fluorescence decay kinetics and resonance Raman spectroscopy.

We report the fluorescence decay kinetics and the vibrational properties of chlorophyll a bound to the 47-kDa antenna protein (CP47) of spinach photosystem II. The chlorophyll fluorescence of CP47 samples decays with four lifetimes (tau = 75.8 ps, 1.05 ns, 3.22 ns, and 5.41 ns). The 75.8-ps and 3.22-ns components are associated with chlorophyll a bound to relatively intact centers, the 1.05-ns component corresponds to chlorophyll bound to centers that are slightly perturbed, and the the 5.41-ns phase probably originates from centers that are severely denatured. The resonance Raman spectrum of CP47 at 441.6 nm (this work) and at 406.7 nm [de Paula, J. C., Ghanotakis, D. F., Bowlby, N. R., Dekker, J. P., Yocum, C. F., & Babcock, G. T. (1990) in Current Research in Photosynthesis (Baltscheffsky, M., Ed.), Vol. I, pp 643-646, Kluwer Academic Publishers, Dordrecht, The Netherlands] shows heterogeneity in the C = O stretching region. This part of the spectrum monitors the environment of the keto group at position 9 of the chlorophyll a molecule. We show that several structurally distinct pools of chlorophyll a are bound to CP47. Four of these may be distinguished by their C9 = O stretching frequencies (nu C = O = 1670, 1688, 1693, and 1701 cm-1). By analyzing the resonance enhancement pattern of these modes, we ascribe the 1693-cm-1 vibration to denatured centers. Of the remaining populations, we propose that the 1670-cm-1 vibration is consistent with a hydrogen bond between the C9 = O group of chlorophyll a and the protein. We elaborate on the role of this chromophore-protein interaction in the mechanism of energy transfer within the 47-kDa antenna protein.

Chlorophyll↗
PubMed1994

Instantaneous helical axis estimation from 3-D video data in neck kinematics for whiplash diagnostics.

To date, the diagnosis of whiplash injuries has been very difficult and largely based on subjective, clinical assessment. The work by Winters and Peles Multiple Muscle Systems--Biomechanics and Movement Organization. Springer, New York (1990) suggests that the use of finite helical axes (FHAs) in the neck may provide an objective assessment tool for neck mobility. Thus, the position of the FHA describing head-trunk motion may allow discrimination between normal and pathological cases such as decreased mobility in particular cervical joints. For noisy, unsmoothed data, the FHAs must be taken over rather large angular intervals if the FHAs are to be reconstructed with sufficient accuracy; in the Winters and Peles study, these intervals were approximately 10 degrees. in order to study the movements' microstructure, the present investigation uses instantaneous helical axes (IHAs) estimated from low-pass smoothed video data. Here, the small-step noise sensitivity of the FHA no longer applies, and proper low-pass filtering allows estimation of the IHA even for small rotation velocity omega of the moving neck. For marker clusters mounted on the head and trunk, technical system validation showed that the IHAs direction dispersions were on the order of one degree, while their position dispersions were on the order of 1 mm, for low-pass cut-off frequencies of a few Hz (the dispersions were calculated from omega-weighted errors, in order to account for the adverse effects of vanishing omega). Various simple, planar models relating the instantaneous, 2-D centre of rotation with the geometry and kinematics of a multi-joint neck model are derived, in order to gauge the utility of the FHA and IHA approaches. Some preliminary results on asymptomatic and pathological subjects are provided, in terms of the 'ruled surface' formed by sampled IHAs and of their piercing points through the mid-sagittal plane during a prescribed flexion-extension movement of the neck.

Adult↗
PubMed1993

Effects of glaucocalyxin A on aggregation and cAMP levels of rabbit platelets in vitro.

Glaucocalyxin A (Gla A) is a new diterpenoid isolated from ethereal extract of the leaves of Rabdosia japonica (Burm f) Hara var glaucocalyx (Maxim) Hara (Labiatae) collected in Northeastern China. When incubated with washed rabbit platelets, Gla A inhibited ADP-, AA-, and PAF-induced aggregation of rabbit platelets with IC50 values of 3.44, 13.32, and 7.74 mumol.L-1, respectively. Gla A 10 and 100 mumol.L-1 increased the cAMP levels in platelets. In combination with imazodan hydrochloride, Gla A (1-100 mumol.L-1) caused a marked increase of platelet cAMP levels, while no effect with PGE1.

Animals↗
PubMed1993

Tamoxifen.

Explore the source record for details and available documents.

Breast Neoplasms↗
PubMed1992

Emergent leadership and female sex role identity.

The effects of female sex role identity on self- and rater evaluations of emergent leadership behavior were compared in two studies. We used the same consensus-seeking procedure in both studies to collect the data; only the biological sex composition of the groups in the second study was changed. Study 1 examined 15 mixed-sex groups of 39 female and 21 male students; Study 2 contained 96 female students in 22 same-sex groups. Sex role orientation was measured with the Bem Sex Role Inventory (BSRI: Bem, 1974). Androgynous and feminine-oriented self-ratings of leadership were significantly higher than peer ratings and were also significantly higher than the undifferentiated self-ratings. The self-ratings of masculine-oriented women agreed most closely with peer ratings. Contrary to research and theory, peer evaluation of leadership behavior by sex role orientation did not differ.

Adult↗