Nuclear synchronization

Rapid stepping of the magnetic field, instead of using a second microwave frequency, has been used to measure interspin distances of the order of 20 A at X-band.28 A microwave pulse, called the pump pulse, is synchronized with the field step and occurs between the second and third pulses of a stimulated echo sequence. The effects of nuclear ESEEM were removed by dividing data obtained with a pump pulse (at the stepped magnetic field) by data obtained without a pump pulse. 

Figure 12.6 Plasmid nuclear localization must precede gene expression. Synchronized TC7 cells were cytoplasmically microinjected with 1000 copies of GFP-expressing plasmids (Dean et al., 1999b). After microinjection, the cells were scored for GFP expression as a function of time. The injected plasmids expressed GFP from the CMV immediate early promoter/enhancer and either contained (open circles) or lacked (closed circles) the SV40 enhancer downstream of the GFP gene. The dotted line represents the time of cell division in this population. As can be seen, plasmids without the SV40 enhancer failed to localize to the nucleus and gave no GFP expression, while plasmids containing the sequence began to express gene product within several hours of cytoplasmic injection.

Plasmid nuclear localization must precede gene expression. Synchronized TC7 cells were 219... 

When the HU synchronization period was finished, and the HU was removed, the seedlings were immediately incubated with 1 mM BOA or water (controls), and the cell cycle was analyzed at different times. Samples (nuclear suspensions) are prepared from root meristems and analyzed by flow cytometry every 2 h during a time period of 12-14 h.15 Comparison of the synchronized-cell cycle progression of BOA-treated plants with that of the corresponding controls allows for detection of partial or total inhibition of the cell cycle. 

Although we interpreted our experimental results with the motion of nuclear packets on the light-dressed ground state of the parent ions, a pump-probe scheme could also explain the pulse width dependence. When two successive pulses are interacted with molecules with a proper interval, the second pulse can be adjusted to achieve synchronicity with the motion of the nuclear wave packet of an excited state. This results in energy transitions to... 

A pulse scheme recovering the zero-quantum Hamiltonian was proposed by Baldus and Meier.142 It is weakly dependent on spectral parameters and a faithful measure of internuclear distances. This sequence is based on the former rotor-synchronized R/L-driven polarization transfer experiments.143,144 It uses the LG or FS-LG, which is used to decouple the high-7 spins, and combined MAS and RF irradiation of low-7 spins to decouple the hetero-nuclear dipolar interactions. With phase-inversion and amplitude attenuation in the rotating frame and refocusing pulses in the laboratory frame part of the pulse sequence, a zero-quantum average Hamiltonian can be obtained with optimum chemical-shift/offset independence. 

A. L. Baker and R. R. Schmidt (1964b). Induced utilization of polyphosphate during nuclear division in synchronously growing Chlorella. Biochim. Biophys. Acta, 93, 180-182. 

In transition state theory, the rate of an adiabatic chemical reaction depends only on the difference between free energy in initial and transition states. From point of view of thermodynamics, formation of an intermediate complex can not give any preference to the process as compared with a collision complex. Nevertheless, the formation of a preliminary (pretransition) structure on the reaction coordinate can constrain the system of nuclear motions that do not lead to reaction products and, therefore, accelerate the process. It is necessary to stress that this acceleration is not caused by entropy reason, but by the optimization of the synchronization factor. 

Another possible two-electron mechanism involves the direct transport of two electrons from a mononuclear transition metal complex to a substrate (S). Such a transport alters sharply the electrostatic states of the systems and obviously requires a substantial rearrangement of the nuclear configuration of ligands and polar solvent molecules. For instance, the estimation of the synchronization factor (asyn) for an octahedral complex, with Eq. 2.44 shows a very low value of asyn = 10 7to 10 8 and, therefore, a very low rate of reaction. The probability of two-electron processes, however, increases sharply if they take place in the coordination sphere of a transition metal, where the reverse compensating electronic shift from the substrate to metal occurs. Involvement of bi- and, especially, polynuclear transition metal complexes and clusters and synchronous proton transfer in the redox processes may essentially decrease the environment reorganization, and, therefore, provide a high rate for the two- electron reactions. 

The multi-electron nature of the energetically favorable process does not evidently impose any new, additional restriction on its velocity. Within a coordination sphere the orbital overlap is effective and, therefore the resonance integral V is high. The strong delocalization of electrons in clusters, polynuclear complexes in clusters and polynuclear complexes reduces to a minimum the reconstitution of the nuclear system during electronic transitions and, therefore, provides a high value for the synchronization factor. 

Melatonin is an indole-derived anterior pituitary hormone that causes downstream inhibition of a-MSH-induced melanogenesis. Melatonin is antiamnesic, synchronizes circadian and circannual rhythms and is metabolized to 5-methoxytryptamine. Melatonin acts via GPCRs MT1 and MT2 (which both couple through Gai and cAMP decrease). MT1 may also couple via Gao and Gaq to activate PLC (and hence increase cytosolic Ca2+) and via G Gy activation of PLA2. Melatonin can further interact with nuclear receptor superfamily orphan retinoid receptors RZR/ROR. Melatonin fluctuates with a circadian rhythm and is elevated in blood during the night. Melatonin is accordingly of social importance in relation to shift work and jet-lag. Melatonin and 5-methoxytryptamine occur in some plants (Table 5.8). 

Fig. 5. Hypothetical scheme for the evolution of heterothallism and secondary homothallism in Mycobionta. For synchronous nuclear division in Benjaminiella multispora, Cokeromyces and Mucor species with respect to primary homothallism, compare Forst and Prillinger [159]. For molecular details, see Hiscock and Kiies [90 and the literature cited therein]. For secondary homothallsim, see Glass et al. [160] and Yun et al. [95]. IC = Intracellular function EC = extracellular function SP = structural proteins which are involved in pheromone binding RP = regulatory proteins which are involved in n-DNA binding and regulation of transcription.

ALA synthase can be suppressed by glucose. Due to the short half-life of ALA synthase of 70-80 minutes, inhibition or induction of this enzyme very quickly affects haem synthesis. Haem deficiency due to an enzyme defect causes an increase in 5-aminolaevulinic acid. Free haem is either integrated into various apoproteins or it intervenes as a haem repressor with the nuclear gene chain, which leads to the formation of specific mRNA for ALA synthase. Synthesis and consumption of haem are synchronized precisely. The organism produces some 300 mg haem per day, with only 1% being excreted unused in the urine or faeces. (271, 273, 300, 309) (s. p. 34) (s. tab. 3.3)... 

Anti-glycating effects. It was shown in 1990 that camosine (50-100 mg/kg body weight) increases survival of rodents when it was administered to animals before sub-lethal dose of y-irradiation [5]. Kurella et al. [58] have found that under these conditions viability of haemopoietic stem cells is significantly increased and their colony forming activity is activated as well. These phenomena can be addressed to anti-radical protection of biomacromolecules by camosine, however camosine was additionally found to protect nuclear DNA from oxidative modification induced by hyperoxia, to preserve its native stmcture and to synchronize cell cycle in vitro [59]. Its addition to the medium where fibroblasts were cultivated increased the longevity of cell life and reversed the senescence features of the cells [60]. Moreover, camosine was demonstrated to increase stability of... 

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