Quantum biology revisited Cao, Jianshu; Cogdell, Richard J; Coker, David F ...
Science advances,
04/2020, Volume:
6, Issue:
14
Journal Article
Peer reviewed
Open access
Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical ...quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.
The observation of persistent oscillatory signals in multidimensional spectra of protein-pigment complexes has spurred a debate on the role of coherence-assisted electronic energy transfer as a key ...operating principle in photosynthesis. Vibronic coupling has recently been proposed as an explanation for the long lifetime of the observed spectral beatings. However, photosynthetic systems are inherently complicated, and tractable studies on simple molecular compounds are needed to fully understand the underlying physics. In this work, we present measurements and calculations on a solvated molecular homodimer with clearly resolvable oscillations in the corresponding two-dimensional spectra. Through analysis of the various contributions to the nonlinear response, we succeed in isolating the signal due to inter-exciton coherence. We find that although calculations predict a prolongation of this coherence due to vibronic coupling, the combination of dynamic disorder and vibrational relaxation leads to a coherence decay on a timescale comparable to the electronic dephasing time.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
JAK2, a member of the Janus kinase super-family was found to interact functionally with Raf-1, a central component of the ras/mitogen-activated protein kinase signal transduction pathway. ...Interferon-$\gamma $ and several other cytokines that are known to activate JAK2 kinase were also found to stimulate Raf-1 kinase activity toward MEK-1 in mammalian cells. In the baculovirus coexpression system, Raf-1 was activated by JAK2 in the presence of p21$^{\text{ras}}$. Under these conditions, a ternary complex of p21$^{\text{ras}}$, JAK2, and Raf-1 was observed. In contrast, in the absence of p21$^{\text{ras}}$, coexpression of JAK2 and Raf-1 resulted in an overall decrease in the Raf-1 kinase activity. In addition, JAK2 phosphorylated Raf-1 at sites different from those phosphorylated by pp60$^{\text{v-src}}$. In mammalian cells treated with either erythropoietin or interferon-$\gamma $, a small fraction of Raf-1 coimmunoprecipitated with JAK2 in lysates of cells in which JAK2 was activated as judged by its state of tyrosine phosphorylation. Taken together, these data suggest that JAK2 and p21$^{\text{ras}}$ cooperate to activate Raf-1.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Corn (Zea mays L.) plants express unexpected K‐deficiency symptoms when grown under certain conservation tillage production systems on high‐K‐testing soils. This field study was conducted to ...determine if K fertilizer treatments interact with P and N planting‐time fertilizer placement treatments to affect crop growth, nutrient composition, and yield in an irrigated no‐till corn production system on high‐K‐testing soil. The 3‐yr study was conducted on Lowry silt loam soils (coarse‐silty, mixed, superactive, mesic Typic Haplustolls) near Pierre, SD. Fertilizer placement (main plot) treatments consisted of P and N fertilizers that were applied with the corn planter to (i) the soil surface, (ii) the seed furrow, or (iii) a band 5 cm to the side of the seed furrow and 5 cm deep. Fertilizer products containing K, also applied at planting time, provided a with‐K subplot comparison with subplots that received no added K fertilizer. Corn plants were sampled for root pull resistance, shoot dry weight, and shoot mineral nutrient composition at the tassel stage of development and grain yield. Data combined over the 3 yr of the study revealed that added K fertilizer had no effect on grain yield and did not interact with P and N fertilizer placement treatments to affect grain yield. When P fertilizer was placed with the seed and N fertilizer was placed in a 5‐ by 5‐cm band, corn plants had 185 kg root−1 pull resistance, 0.26 g shoot−1 P accumulation, and 10.5 Mg ha−1 grain yield. However, when P and N fertilizers were applied to the soil surface, corn plants had significantly less root pull resistance (151 kg root−1), P accumulation (0.22 g P shoot−1) and grain yield (10.1 Mg ha−1). Added K fertilizer decreased shoot dry weight (added K = 97 g shoot−1, no K = 103 g), decreased P accumulation (added K = 0.22 g P plant−1, no K = 0.25 g), increased shoot N concentration (added K = 19.3 mg N g−1, no K = 19.0 mg), and had no significant effect on K concentration or accumulation. We conclude that, although planting‐time fertilizer placement was important for optimum corn growth and yield production in irrigated no‐till systems, added K fertilizer did not interact with fertilizer placement to improve yield on the high‐K‐testing soils used in this study.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Ultrafast photochemical reactions are initiated by vibronic transitions from the reactant ground state to the excited potential energy surface, directly populating excited-state vibrational modes. ...The primary photochemical reaction of vision, the isomerization of retinal in the protein rhodopsin, is known to be a vibrationally coherent reaction, but the Franck–Condon factors responsible for initiating the process have been difficult to resolve with conventional time-resolved spectroscopies. Here we employ experimental and theoretical 2D photon echo spectroscopy to directly resolve for the first time the Franck–Condon factors that initiate isomerization on the excited potential energy surface and track the reaction dynamics. The spectral dynamics reveal vibrationally coherent isomerization occurring on the fastest possible time scale, that of a single period of the local torsional reaction coordinate. We successfully model this process as coherent wavepacket motion through a conical intersection on a ∼30 fs time scale, confirming the reaction coordinate as a local torsional coordinate with a frequency of ∼570 cm–1. As a result of spectral features being spread out along two frequency coordinates, we unambiguously assign reactant and product states following passage through the conical intersection, which reveal the key vibronic transitions that initiate the vibrationally coherent photochemistry of vision.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Stimulation of the erythropoietin receptor (EPO-R) or the interleukin-2 receptor (IL-2-R) by their respective ligands has been reported to activate tyrosine phosphorylation of the cytoplasmic ...protein, Shc. We have recently characterized a cell line, CTLL-EPO-R, that contains functional cell-surface receptors for both EPO and IL-2. Although stimulation with IL-2 or IL-15 resulted in the rapid, dose-dependent tyrosine phosphorylation of Shc, stimulation with EPO failed to activate Shc. EPO, IL-2, and IL-15 activated the tyrosine phosphorylation of the adaptor protein, Shp2, and the association of Shp2/Grb2/cytokine receptor complexes. In addition, EPO, IL-2, and IL-15 activated Raf1 and ERK2, demonstrating that the Raf1/MEK/MAP kinase pathway was activated. These results indicate that multiple biochemical pathways are capable of conferring a mitogenic signal in CTLL-EPO-R. EPO can activate the Raf1/MEK/ MAP kinase pathway via Shc-dependent or Shc-independent pathways, and Shc activation is not required for EPO-dependent cell growth in CTLL-EPO-R.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Physical activity may be constrained or facilitated by local environments. The availability of neighborhood facilities for physical activity may be particularly relevant for youth, who are unable to ...drive and whose activity is often limited to the immediate distance they are able to walk or bicycle. Several studies have shown that proximity to recreational facilities and parks is one of the most important predictors of physical activity. Because the United States already has an extensive infrastructure of parks, with 70% of adults indicating that they live within walking distance of a park or playground, parks may be a potential venue for increasing physical activity. This might be particularly important for adolescent girls, whose physical activity levels decline substantially as they go through puberty. The goal of this study was to examine the association between park proximity, park type, and park features and physical activity in adolescent girls.
This was a cross-sectional study using baseline data from the Trial of Activity for Adolescent Girls. It included 1556 grade 6 girls who were randomly selected from 6 middle schools in each of the following 6 field site areas: Washington, DC, and Baltimore, Maryland; Columbia, South Carolina; Minneapolis, Minnesota; New Orleans, Louisiana; Tucson, Arizona; and San Diego, California. Girls wore accelerometers for 6 days to measure metabolic equivalent-weighted moderate-to-vigorous physical activity, a measure accounting for the volume and intensity of activity. Metabolic equivalent-weighted moderate-to-vigorous physical activity was calculated for the hours outside of school time using 2 different cutpoints, activity levels > or = 3.0 metabolic equivalents and > or = 4.6 metabolic equivalents, the latter indicating activity at the intensity of a brisk walk or higher. We mapped all of the parks within 1 mile of each girl's home. Trained staff used a checklist to document the presence of facilities and amenities at each park, including passive amenities, such as drinking fountains, restrooms, and areas with shade, as well as active amenities like basketball courts, multipurpose fields, playgrounds, and tennis courts.
Mean nonschool metabolic equivalent-weighted moderate/vigorous physical activity, using the 4.6 metabolic equivalent cutoff, was 611.1 minutes (range: 49.7-4718.6 metabolic equivalent minutes per 6 days) and 1704.8 metabolic equivalent minutes per 6 days (range: 276.2-5792.6 metabolic equivalent minutes per 6 days) when using the 3.0 metabolic equivalent cutpoint. Many girls had multiple parks within a 1-mile radius of their homes: 57% had > or = 1 type of park, the majority being neighborhood or community parks; 42% had between 1 and 3 parks, 37% had > or = 4 parks, and 14% had > or = 8 parks. The type, number, and specific parks features were associated with girls' nonschool metabolic equivalent-weighted moderate/vigorous physical activity. At the 4.6 metabolic equivalent cutpoint, higher levels of nonschool metabolic equivalent-weighted moderate/vigorous physical activity were associated with both neighborhood and community parks (22 metabolic equivalent minutes) and miniparks (40 metabolic equivalent minutes). Each park, regardless of type, in the half-mile around each girl's home was associated with an increase in nonschool metabolic equivalent-weighted moderate/vigorous physical activity by 2.8% or 17.2 nonschool minutes of metabolic equivalent-weighted moderate/vigorous physical activity per 6 days. Beyond a half-mile, each park increased nonschool metabolic equivalent-weighted moderate/vigorous physical activity by 1.1% or 6.7 metabolic equivalent minutes per 6 days. For the average girl with 3.5 parks within a 1-mile radius of home, the presence of parks accounted for 36.5 extra nonschool metabolic equivalent minutes per 6 days, approximately 6% of total nonschool metabolic equivalent-weighted moderate/vigorous physical activity. Using the 3.0 metabolic equivalent cutpoint, this sums to an additional 68 metabolic equivalent minutes of nonschool metabolic equivalent-weighted moderate/vigorous physical activity over 6 days, or 4% of the total. The most common amenities in the parks were playgrounds, multipurpose fields, and picnic areas. Slightly more than one third of girls lived within a half-mile of a park with a basketball court, and > 20% had access to walking paths and tennis courts in their local park. Higher levels of nonschool metabolic equivalent-weighted moderate/vigorous physical activity per 6 days were associated with walking paths (13 metabolic equivalent minutes), running tracks (82 metabolic equivalent minutes), playgrounds (28 metabolic equivalent minutes), and basketball courts (30 metabolic equivalent minutes). Parks with streetlights and floodlights were also associated with an increase of 18 and 22 minutes of nonschool metabolic equivalent-weighted moderate/vigorous physical activity, respectively. With the 3.0 metabolic equivalent cutoff for metabolic equivalent-weighted moderate/vigorous physical activity, additional nonschool metabolic equivalent minutes more than doubled when girls had miniparks (92 metabolic equivalent minutes), natural resource areas (36 metabolic equivalent minutes), walking paths (59 metabolic equivalent minutes), and running tracks (208 metabolic equivalent minutes) within a half-mile of their homes. Skateboard areas and special-use parks were negatively associated with nonschool metabolic equivalent-weighted moderate/vigorous physical activity in adolescent girls.
Adolescent girls who live near more parks, particularly near those with amenities that are conducive to walking and with active features, engage in more nonschool metabolic equivalent-weighted moderate/vigorous physical activity than those with fewer parks. Whether this is because of actual use of the parks or neighborhood choice could not be determined. Although the magnitude of the association between parks and additional minutes of metabolic equivalent-weighted moderate/vigorous physical activity was small for an individual, amounting to an average of 4%-6% of a girl's total nonschool metabolic equivalent-weighted moderate/vigorous physical activity, it is likely to have a large population-level association. Because of the potential population level impact, the use of parks to promote physical activity should be further studied.
PDF
