There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

The genetic and biochemical networks which underlie such things as homeostasis in metabolism and the developmental programs of living cells, must withstand considerable variations and random perturbations of biochemical parameters These occur as transient changes in, for example, transcription, translation, and RNA and protein degradation The intensity and duration of these perturbations differ between cells in a population The unique state of cells, and thus the diversity in a population, is owing to the different environmental stimuli the individual cells experience and the inherent stochastic nature of biochemical processes (for example, refs 5 and 6) It has been proposed, but not demonstrated, that autoregulatory, negative feedback loops in gene circuits provide stability, thereby limiting the range over which the concentrations of network components fluctuate Here we have designed and constructed simple gene circuits consisting of a regulator and transcriptional repressor modules in Escherichia coli and we show the gain of stability produced by negative feedback

Engineering stability in gene networks by autoregulation

1. Electron Donor 2223 2. Electron Transfer Path 2225 3. Electron Transfer Mechanism 2226 4. Physiological Relevance 2226 D. Radical Reactions in Photolyase 2226 E. “Dark Function” of Photolyase 2227 F. Regulation of Photolyase 2227 III. (6−4) Photolyase 2228 IV. Cryptochromes 2230 A. Structure 2231 B. Function 2231 1. Circadian Rythm 2231 2. Mammalian Circadian System 2231 3. Cryptochromes and the Circadian Clock 2232 V. Perspectives 2234 VI. Acknowledgment 2235 VII. References 2235

Structure and function of DNA photolyase and cryptochrome blue-light photoreceptors.

Cryptochromes are blue, ultraviolet-A photoreceptors. They were first characterized for Arabidopsis and are also found in ferns and algae; they appear to be ubiquitous in the plant kingdom. They are flavoproteins similar in sequence to photolyases, their presumptive evolutionary ancestors. Cryptochromes mediate a variety of light responses, including entrainment of circadian rhythms in Arabidopsis, Drosophila, and mammals. Sequence comparison indicates that the plant and animal cryptochrome families have distinct evolutionary histories, with the plant cryptochromes being of ancient evolutionary origin and the animal cryptochromes having evolved relatively recently. This process of repeated evolution may have coincided with the origin in animals of a modified circadian clock based on the PERIOD, TIMELESS, CLOCK, and CYCLE proteins.

https://science.sciencemag.org/content/sci/284/5415/760.full.pdf

Cryptochromes: Blue Light Receptors for Plants and Animals

Ultrafast dynamics of carotenoid excited States-from solution to natural and artificial systems.

Escherichia coli DNA photolyase, which photorepairs cyclobutane pyrimidine dimers, contains two chromophore cofactors, 1,5-dihydroflavin adenine dinucleotide (FADH2) and 5,10-methenyltetrahydrofolate (MTHF). Previous work has shown that MTHF is the primary photoreceptor which transfers energy to the FADH2 cofactor; the FADH2 singlet excited state then repairs the photodimer by electron transfer. In this study, we have determined the rate constants for these photophysical processes by time-resolved fluorescence and absorption spectroscopy. From time-resolved fluorescence, we find that energy transfer from MTHF to FADH2 and FADH degrees occurs at rates of 4.6 x 10(9) and 3.0 x 10(10) s-1, respectively, and electron transfer from FADH2 to a pyrimidine dimer occurs at a rate of 5.5 x 10(9) s-1. Using Forster theory for long-range energy transfer and assuming K2 = 2/3, the interchromophore distances were estimated to be 22 A in the case of the MTHF-FADH2 pair and 21 A for the MTHF-FADH degrees pair. Picosecond absorption spectroscopy identified an MTHF single state which decays to yield the first excited singlet state of FADH2. The lifetimes of MTHF and FADH2 singlets and the rates of interchromophore energy transfer, as well as the rate of electron transfer from FADH2 to DNA measured by time-resolved fluorescence, were in excellent agreement with the values obtained by picosecond laser flash photolysis. Similarly, fluorescence or absorption lifetime studies of the folate-depleted enzyme with and without photodimer suggest that FADH2, in its singlet excited state, transfers an electron to the dimer with 89% efficiency. The distance between FADH2 and the photodimer was calculated to be ca. 14 A.

Determination of rates and yields of interchromophore (folate----flavin) energy transfer and intermolecular (flavin----DNA) electron transfer in Escherichia coli photolyase by time-resolved fluorescence and absorption spectroscopy.

Picosecond Laser Photolysis Studies on the Photorepair of Pyrimidine Dimers by DNA Photolyase. 1. Laser Photolysis of Photolyase-2-Deoxyuridine Dinucleotide Photodimer Complex

Time-resolved absorption spectra, upon excitation of the all-trans, 9-cis, 13-cis, and 15-cis isomers of {beta}-carotene, were recorded by using 20-25-ps, 355-nm pump and white-continuum interrogating pulses. The isomers showed the S{sub n} {l arrow} S{sub 1} absorption at 556 (all-trans), 565 (9-cis), 560 (13-cis), and 562 (15-cis) nm; no time-dependent changes of the absorptions were detected. (The S{sub 1} lifetimes for the all-trans and 15-cis isomers were determined precisely, by using 0.5-ps pump and interrogating pulses, to be 12.4 {plus minus} 0.5 and 14.0 {plus minus} 0.5 ps, respectively.) After the decay of the S{sub n} {l arrow} S{sub 1} absorption, a weak absorption ascribable to the T{sub n} {l arrow} T{sub 1} transition remained in the 510-520-nm region, from which the quantum yield of intersystem crossing was estimated to be on the order of 10{sup {minus}3}. Transient Raman spectra were recorded by using 355-nm pump and 532-nm probe mode-locked (76 MHz), Q-switched (800 Hz) pulse trains (pulse duration {approximately} 100 ps). An S{sub 1} Raman spectrum was extracted by subtraction between a pair of pump-and-probe spectra with different delay times, i.e. 0 and 500 ps. A T{sub 1} Raman spectrum was extracted by subtracting a probe-only spectrum from amore » pump-and-probe spectrum with the delay time 500 ps. Each isomer showed a unique S{sub 1} Raman spectrum, which was interpreted by assuming the configuration of the particular isomer. On the other hand, the 13-cis and 15-cis isomers showed T{sub 1} Raman spectra that are essentially the same as that shown by the all-trans isomer, the 9-cis isomer showed a unique T{sub 1} Raman spectrum. The above results indicate (1) that no isomerization takes place in the S{sub 1} state and (2) that the T{sub 1} state is generated through intersystem crossing.« less

S1 and T1 species of .beta.-carotene generated by direct photoexcitation from the all-trans, 9-cis, 13-cis, and 15-cis isomers as revealed by picosecond transient absorption and transient Raman spectroscopies

This paper discusses the measurement of picosecond time-resolved absorption spectrum measurements of diphenylacetylene in various solvents. S{sub n}{l_arrow}S{sub 1} transition caused bands at 435 and 700 nm while absorption from a second excited singlet state (S{sub 2}) caused a band at 500 nm, which was the fluorescence state of DPA. The 500 nm band has and Arrhenius type temperature dependence but the S{sub 1} did not. Turnover of the S{sub 1}-S{sub 2} coupling may explain the large temperature effect of the S{sub 2} state lifetime. 13 refs., 7 figs., 2 tabs.

Picosecond time-resolved absorption spectrum measurements of the higher excited singlet state of diphenylacetylene in the solution phase

Photoinduced charge separation by chromophores encapsulated in the hydrophobic compartment of amphiphilic polyelectrolytes with various aliphatic hydrocarbons

Yoshinori Hirata

Papers

Determination of rates and yields of interchromophore (folate----flavin) energy transfer and intermolecular (flavin----DNA) electron transfer in Escherichia coli photolyase by time-resolved fluorescence and absorption spectroscopy.

Picosecond Laser Photolysis Studies on the Photorepair of Pyrimidine Dimers by DNA Photolyase. 1. Laser Photolysis of Photolyase-2-Deoxyuridine Dinucleotide Photodimer Complex

S1 and T1 species of .beta.-carotene generated by direct photoexcitation from the all-trans, 9-cis, 13-cis, and 15-cis isomers as revealed by picosecond transient absorption and transient Raman spectroscopies

Picosecond time-resolved absorption spectrum measurements of the higher excited singlet state of diphenylacetylene in the solution phase

Photoinduced charge separation by chromophores encapsulated in the hydrophobic compartment of amphiphilic polyelectrolytes with various aliphatic hydrocarbons