A CENTURY OF PHOTOBIOLOGY

Thomas P. Coohill

Department of Physics
Siena College, Loudonville, NY 12211-1462
tcoohill@siena.edu

An Apology and an Explanation
This chapter derives from a presentation at the 13th International Congress on Photobiology meeting of the Association Internationale de Photobiologie [AIP, now IUPB (see table 18)] in San Francisco, USA, July 2000, updated in April 2008. It, therefore, will be broad and topical rather than detailed. I will highlight the progress of certain fields through example rather than attempt a comprehensive review of any of them. To review the results of such a wide area of research would require several volumes. The few pages presented here can only be a severely limited synopsis of major achievements. The work of a few researchers will be emphasized. It is certain that some areas will be neglected due to the limited knowledge of the author. It will be clear that Photobiology will be highlighted whereas Photochemistry will be interspersed under the separate headings, e.g., citing the role of singlet oxygen in the table for photodynamic treatment. The past will be emphasized over the present since it easier to sort out. It is with a great deal of trepidation that I attempt even this limited summary. Major areas of research and major contributors to each field will be left unmentioned. Apologies are no substitute for ignorance but may assuage the ire of some. I hope that I have cited people's work correctly.

Photobiology
Table 1 lists some advantages of using light to study biological processes (Jagger, 1967). Photobiological techniques are sometimes less invasive than those used in other areas of science, allowing the sample to respond without incurring much damage. It is no coincidence that two of the most important macromolecules in biology - DNA and chlorophyll - respond readily to light. In fact absorption of light by plants is the driving force for much of the life on earth. Accordingly, studies involving these two molecules and human responses dominated early work in Photobiology. As we will see below, additional research areas also utilized light effects, thus broadening Photobiology into a truly cross-disciplinary science. Thus, photobiologists are found in many occupations; from agriculture to physics and chemistry; from oceanography to medicine. So it is expected that they have made significant progress this past century.

Table 1. Some advantages to using light to study biological processes

many bio-molecules (e.g., DNA, chlorophyll) absorb and are affected by light
the target chromophores are sometimes well known
the photochemistry of many bio-processes is well understood
some photoprocesses can be elicited without causing permanent cellular damage
light treatment is not necessarily toxic
light treatment is harmless to molecules that do not absorb at the source wavelengths (the photon has to be absorbed to cause an effect)
therefore, light penetration into cells and tissues need not be invasive
light sources are often inexpensive and easy to operate and quantify.

Finsen - 1900 - Light as Therapy
Photobiology progressed along several fronts starting in 1900. Human responses to solar radiation dominated the early concerns, not, as is currently in vogue, due to its harmful effects, but rather, due to its therapeutic use. So, it is easy to choose the first photobiologist to mention in any review of the century - Niels Ryberg Finsen. Finsen saw the value of exposing patients to the sun to treat a variety of diseases, such as lupus lupus vulgaris (skin tuberculosis - Finsen, 1900). He first made a large glass lens to focus the sun's rays and employed a copper sulfate solution as a filter (which eliminated the UV-B). It worked to some extent. He then decided it would be easier to set up an indoor clinic and expose patients to the output of a powerful carbon arc lamp - thereby adding back the UV-B. This intense light treatment was successful in many cases and started the new field of phototherapy. For this work, Finsen was awarded the third Nobel Prize in physiology and medicine in 1903. The citation stated:

in recognition of his contribution to the treatment of diseases,
especially lupus vulgaris, with concentrated light radiation,
whereby he has opened a new avenue for medical science.


Table 2. Finsen Medalists 1937-2004

1937	Corno	Switzerland	1976	Blum	USA
1951	Rollier	Switzerland		Hendricks	USA
	Jausion	France		Shugar	Poland
1954	Coblentz	USA	1980	Setlow	USA
1959	Rottier	Netherlands	1984	Smith	USA
	Terenin	USSR		Haupt	Germany
	Rupert	USA	1988	Magnus	UK
1968	Hollaender	USA		Arnon	USA
	Bowen	UK	1992	Urbach	USA
	Stiles	UK		Stoeckenius	USA
1972	Forster	Germany	1996	Van der Leun	Netherlands
	Hill	UK		Kondo	Japan
	Latarjet	France	2000	Yoshizawa	Japan
				Briggs	USA
	Latarjet	France	2004	Epstein	USA
				Furuya	Japan

We honor him by awarding a prominent researcher the Finsen Medal every four years and by the establishment of the Finsen Lecture series at IUPB international meetings.


Table 3. Finsen Lectures 1980-2004

1980	Junge	Germany
1984	Vogelmann	Sweden
1988	Ley	USA
1992	Satoh	Japan
1996	Brash	USA
	Schwarz	Germany
2000	Petrich	USA
2004	Yarosh	USA

Thus began the era of heliotherapy and the solarium, the building of mountain retreats for the phototherapy of guests and the widespread belief that exposure to sunlight was healthy and invigorating.

For convenience, intensity and spectral purity, better light sources were developed as the century progressed.


Table 4. Phototherapy

1870	description of XP	Kaposi

1900 to World War II - The Glory Days of Phototherapy

1900	TB treatment	Finsen (Nobel Prize)
1911	transmission into skin	Hassalbach, Chance, Yodh, Patterson, Gratton
1919	rickets treatment	Huldschinsky
1925	UV causes vitamin D production	Steenbock, Daniels

After World War II, Pills Replace Photons until UVA treatment emerged

1970	psoriasis	Fitzpatrick, Parrish, Pathak, Wolf, Hönigsmann
1980	photodynamic therapy, photomedicine	Dougherty, Kessel, Hearst, Dall'Acqua, Rodighiero, Averbeck, Gasparro
1997	Excimer laser (psoriasis, vitiligo)	Bónis, Kemény, Dobozy Anderson, Taylor

Table 5. Tools

5x10⁹B.C.	sun	God, Bernhardt, Rollier, Dorno, Saidman
1850-1990	artificial sources; carbon, Hg, xenon	Finsen, Kromayer
1666; 1859	spectroscope	Newton; Kirckhoff, Bunsen
1880	monochromator	Wadsworth, Magnus, Latarjet, Saidman, Johns
1960	laser	Sorokin, Wynne, Berns, Ashkin, Anderson, Taroni
1980	synchrotron radiation	Ito, Sutherland, Munro

lenses, prisms, filters…plus numerous chemical and biological devices and assay methods

Hausser, Human Skin and the Beginnings of Action Spectroscopy
It was because he was diagnosed with tuberculosis that the German physicist Hausser went to a heliotherapy retreat in the Alps. Hausser (Hausser and Vahle, 1927, 1969) noted that "a long hike on a glacier, in the afternoon hours under a burning sun had almost no effect, while … a brief sojourn on snow at noontime resulted in a severe sunburn." This observation led him to construct the first true action spectrum (of the kind now widely used) for erythema. The importance of this work cannot be over emphasized. It was the first detailed examination of a biological effect as a function of wavelength, and pointed to the beginnings of a means for determining the molecule(s) responsible for that effect. Hausser realized the difficulties that humans posed as laboratory subjects and switched to bananas. His photo of the mercury spectrum singed into the skin of a banana (Hausser and Oehmcke, 1933) remains one of the most convincing simple displays of biological response to individual wavelengths. Hausser's work was careful enough and employed proper controls to also allow him to discover the phenomenon of photoreactivation of short wavelength UV damage by subsequent exposure to radiation of longer wavelength (Hausser and Vahle, 1931). After Hausser there was steady progress in examining the effects of light (mainly UV) on human skin, much of it centered on unraveling the role of light in photocarcinogenesis. Blum (1959) and others (Urbach, 1993 and 1997; Urbach, et al., 1976) spearheaded this drive, the results of which are summarized in Table 6. Owing to the difficulty of human subject research and the variation in response of people with different colored skin, much of the progress in determining the true action spectrum for human skin cancer was done with animal models, especially a genetically constructed strain of hairless mice. It was only in 1994 that a generally accepted action spectrum for photocarcinogenesis was agreed upon (De Gruijl and van der Leun, 1994).


Table 6. Human Skin 1900-2000

it's the Ultraviolet that burns	Charcot, Unna, Hausser…
ultraviolet can tan	Unna, Hausser, Vahle…
ultraviolet can cause cancer	Dubreuilh, Findlay, Roffo, Blum, Urbach…
action spectrum for carcinogenesis	Coblentz, Urbach, Forbes, Van der Leun, De Gruijl….

Gates and Molecular Biology
In the 1920s, when Hausser's action spectrum for human skin appeared, progress was made on a second front. F. L. Gates at the Rockefeller Institute tested the notion that the shorter the UV wavelength the more effective it was in killing cells. He introduced several important constraints to the field of light research, for example, the importance of ensuring that the target chromophores were exposed to the same fluence from the source. He worked with a layer of bacteria "so transparent that objects may be seen through it clearly and without distortion…" (Gates, 1930). This ensured that the whole sample was exposed to the same fluence of light. Using a monochromator he was able to irradiate samples with wavelengths as short as 225 nm. He noted that the killing effect on a per photon basis peaked in the region of maximum nucleic acid absorption (265 nm), not at 280 nm where proteins absorb most. This was surprising since, at the time, proteins were believed to be the genetic material. But, if they were, why didn't the action spectrum for killing track with the absorption spectrum for protein? Gates, somewhat tentatively, noted that "it has not escaped our attention that nucleic acid may be the genetic material" (Gates 1928). This (along with later results involving cell mutation) was the first clear indication that nucleic acid (later shown to be DNA) was the genetic material. Even so, this notion was not widely accepted by the biological community until the 1940s. But Gates' work also opened the era of utilizing microorganisms to study molecular events that caused cellular response which, in certain ways, led to the development of the field of molecular biology. As Table 7 shows, this line of research was the first to show that DNA was the genetic material, that it was easily damaged (a bit of a surprise), and that it was readily repaired (more surprising). Contributors were many (McLaren and Shugar, 1964; Setlow, 1968 and 1989; Smith and Hanawalt, 1969; Hanawalt, 1989).


Table 7. Molecular Biology

1930's	DNA is the genetic material	Gates, Muller, Stadler, Hollander…
1940's	DNA is easily damaged	Beukers & Berends, the Setlows…
1950's	DNA is readily repaired	Roberts, Aldous, Setlow, Carrier, Kelner Rupert, Jagger, Sancar, Hanawalt…
1970's	repaired DNA can lead to mutation	Weigle, Devoret, Witkin, Das Gupta…

In addition, molecular biology contributed to the understanding of the molecular basis for human diseases, such as Xeroderma pigmentosum (Cleaver, 1968), launching a photobiologist (Cleaver) to the pages of People Magazine (May 14, 1990), and the National Enquirer (April 26, 1988).

Raab and the Lab Window: Photodynamic Therapy
In 1900 Oscar Raab, working in the laboratory of Van Tappeiner, discovered that certain dyes killed paramecia with greater efficiency in dishes that were placed near the lab window (Raab, 1900). He correctly assumed, and then tested, that it was sunlight streaming through the panes that activated the dye to produce deleterious effects - photodynamic action. This "lab window" effect has been noted several times, including a "re-discovery" of photoreactivation by Kelner in 1949. Meyer-Betz (1913) self-tested photodynamic action when he drank a solution of hematoporphyrin and went out into the sunlight. The dramatic photos of his skin reaction before and after exposure left no doubt that certain compounds could have major photobiologial effects.


Table 8. XP: A Photosensitive Human Disease

1870	description of the disease	Kaposi
1889	solar radiation is the cause	Pringle
1968	due to defective repair of dimers	Cleaver
1970	complementation groups	Kraemer
1991	UV induced mutations in p53 gene	Brash
1996	UV-B and UV-A important	Sarasin

This notion quickly passed into the popular literature. Haggard (1939) in " The Light That Kills:" had the protagonists in a memorable short story die writhing in pain after drinking a photosensitizer and then being exposed to the sun at solar noon.

A new Fifth Horseman, clad in the shining armor of a new science,
rode along in the radiant heavens, carrying in his hand a weapon
which no man or beast would ever be able to defy.

But, even into the 1970's reviewers of grants would stated "We all know that light does not penetrate tissues." Recent advances in photodynamic therapy (PDT), like those shown in Table 9, have made PDT more acceptable to the scientific community (Blum, 1964; Spikes, 1985 and 1997; Fritsch, et al., 1998; Bethea, et al., 1999). PDT is now widely used in medicine and further applications are being discovered every year.


Table 9. Photodynamic Treatment

1888	alkaloids plus light kill better	Marccaci
1898	dyes kill better at certain times of day with light from the window	Raab
1900	therapeutic potential of PDT	Tappeiner
1913	photosensitizes himself	Meyer-Betz
1940	fundamental theories	Blum
1950	molecular biology and photochemistry	Spikes
1961	uses for tumor detection and therapy	Lipson
1964	role of singlet oxygen	Foote
1978	clinical trials	Dougherty, Schwartz, Moan, Kato, Kessel, Levy, Hönigsmann

Plants, the First Photobiological Samples
We have already discussed the role of Photobiology in elucidating the function of DNA, but it was studies in the nineteenth century on the chlorophyll in plants that really started the whole field (Coohill, 1989). This last century has seen remarkable progress in the understanding of the molecular mechanisms that underlie photosynthesis (Govindjee, 1982; Deisenhofer and Norris, 1993; Blankenship, Madigan and Bauer, 1995; Loach, 1997). Since 2000, the PSII structure (Zouni, et al., 2001; Kamiya and Shen, 2003; Biesiadka, et al., 2004; Ferraira, et al., 2004; Loll, et al., 2005) and the oxygen evolving complex (OEC- Barber, 2008) have been elucidated. The photoreceptor complex (containing the LH1 and RC) of photosynthetic bacteria has been characterized (Roszak, et al, 2003). Table 10 briefly high-lights the major contributions that have driven the field. The practical implications of this re-search are enormous and underpin efforts to support a burgeoning world population that has more than quadrupled in the last 100 years. This field is so vast that any attempt to summarize it here would be futile. The table below is offered as a minimal attempt.


Table 10. Photosynthesis

1900s	oxygen evolution from plants	Englemann
1930s	action spectra	Emerson and Arnold
1950s	carbon dioxide fixation and reduction pathway	Calvin (Nobel Prize), Bassham, Benson
1960s	light induced absorbance and EPR changes	Duysens, Witt, Chance, Clayton, Commoner, Calvin
	unmasking the reaction center	Kok, Clayton, Loach
	chemiosmotic effects	Mitchell (Nobel Prize), Jagendorf
	CO2 binding to the RC of PS II, luminescence	Govindjee
1970s	chemistry of reaction centers	Kok, Clayton, Loach, Feher
	four excitations for oxygen evolution	Kok, Joliot
	carotenoids protect plants from photosensitization	Sistrom, Mathews-Roth, Krinsky
1980s	isolation of RCs and light harvesting complexes	Reed, Clayton, Gingras,Thomber, Okamura, Feher, Cogdell
	structure of the bacterial RC	Michel, Deisenhofer (Nobel Prize)
	electron transport theory	Marcus (Nobel Prize)
	time resolved spectroscopy	Rentzipis, Windsor, Parson, Shuvalov
1990s	B820 subunit of LHs	Parkes-Loach and Loach
	reconstitution of LHs	Parkes-Loach and Loach, Schmidt and Paulsen
	structure of bacterial LH2	Cogdell and Michel
	structure of PS1	Witt
2000's	structure of PSII and OEC	Barber, Zouni, Saenger, Kem, Biesiadka, Loll
	photoreceptor cojmplex (LH1 and RC)	Cogdell

Other Human Exposure
We have already discussed the Photobiology of skin exposure, but two other human responses to light also stand out; the eye and immunology.

A) The Eye - It was expected that light would have great influence on the eye, even beyond that of vision. And indeed, neuroendicrine regulation mediated through the eyes and other photoreceptors is well defined (Kochendoefer, et al., 1999; Brainard, 1998; Brainard and Bernecker, 1996; Klein, et al., 1991; Lam, 1996; Wetterberg, 1993; Birge, 1990; Nathans, 1992). Table 11 lists a few landmarks.


Table 11. Human Vision / Neuroendocrine Regulation

1922	mammalian circadian rhythms synchronized by light	Richter
1950s	work with color blind people; light isomerizes rhodopsin	Wald, Hubbard, Yoshizawa
1956	mammalian pineal gland receives light input from eyes	Quay
1960	light damages the lens	Zigman
1965	mammalian reproductive regulation by light	Hoffman, Reiter
	mammalian circadian pacemaker located in hypothalamus	Richter
1980	light induced melatonin suppression in humans	Lewy
1981-1988	role of cyclic GMP in visual signal transduction	Stryer
1983	amino acid sequence of opsin determined	Ovchinikov, Hargrave
1984	light treatment of seasonal affective disorder	Rosenthal
1986	light resetting of human circadian rhythms	Czeisler
1986-1989	genes for color vision cloned	Nathans
1990	ultra fast photoisomerization of rhodopsin	Rentzepis, Shank, Atkinson, Alfano, Callender, Mathies
	transmembrane structure and light induced conformation changes in rhodopsin	Yoshizawa, Hargrave, Khorana, Hubbell, Rothschild, Dickerson
1994	time scale of transition of visual pigment is 200 femtoseconds (fastest reaction in all of biology)	Mathies, Shank
	chemical mechanism for wavelength regulation in cones	Mathies, Sakman

B) Immune Responses - The surprising discovery in the 1970s that ultraviolet radiation caused human immune suppression led to a series of studies looking for the chromophore in skin that causes the response (Kripke, 1986; Noonan and DeFabo, 1992; Duthie, et al., 1999). This phenomenon occurs at lower exposures than those needed to cause erythema (Young, 2000) and may be part of the body's mechanism for not rejecting sunburn damaged cells. With the current focus on allergies in developed countries, it is expected that more will be heard from this field.


Table 12. Photoimmunology

1976	UV alters the immune response preventing rejection of UV tumors	Fisher and Kripke, Daynes
1979	UVB is the effective waveband	De Fabo and Kripke
1979	UV alters antigen presentation	Greene, Stingl, Bergstresser and Streilein
1983	action spectrum indicates UCA photoreceptor	De Fabo and Noonan
1986	UV-epidermal cytokines, immunosuppression	Schwarz and Luger
1987	Cis-UCA initiates immunosuppression	Norval, Howie and Ross, Reeve
1989	UV-DNA lesions, and immunosuppression	Applegate, Ley and Kripke
1995-1998	neuropeptide; mast cell involvement	Gillardon, Hart.

Bioluminescence
Bioluminescence occurs in a living organism when part of the energy from a highly exergonic chemical reaction produces a molecular excited state, which is depopulated by the emission of a photon. At first believed to be a bit arcane, this field helped unravel several biological mysteries, including the phenomenon of "quorum sensing," i.e., chemical communication between bacteria. This in turn has led to advances and insights into important areas such as symbiosis and pathogenesis (Harvey, 1952; Hastings and Morin, 1991; Wilson and Hastings, 1998).


Table 13. Bioluminescence

1947	ATP required for firefly bioluminescence	McElroy
1953	flavin required for bacterial luminescence	Hastings, McElroy
1961	structure of firefly luciferin	White, McCapra
1962	aequorin luminescence in extracts without oxygen triggered by calcium	Shimomura, Johnson
1965	chemiluminescence of excited singlet oxygen	Khan, Kasha, Seliger
1969	chemiluminescence of dioxetanes and dioxetanones	Kopecky, Mumford
1970	autoinduction of bacterial luciferase and quorum sensing	Nealson, Hastings
1971	green fluorescent protein and energy transfer in luminescence	Hastings, Morin
1983	cloning of bacterial luciferase gene and lux operon	Nealson
1986	cloning of firefly luciferase, transgenic expression	DeLuca, Wood
1987	the scintillon; cell organelle in dinoflagellate luminescence	Nicolas, Hastings
1989	tetrapyrrole structure of dinoflagellate luciferin	Nakamura, Kishi, Hastings
1990	structure of green fluorescent protein and cloning of genes	Ward, Prasner, Cormier
1992	use of luciferases for reporting gene expression	Kay, Wood, Johnson
1995	use of green fluorescent protein as a reporter of gene expression	Chalfie

Biological Clocks
Organisms from bacteria to mammals, including humans, respond to periodic illumina-tion by a mechanism of internal clocks (Hastings, et al., 1991; Dunlap, 1996). As prevalent as they are, widespread acceptance of their existence was slow in coming. Due to the pioneering efforts of the individuals listed in the table below, the general public is now well aware of clock biology. Store shelves are full of melatonin, sleep masks are sold in every airport, and shift workers are warned of the disruptions their work schedules may inflict on their lives.

Photomorphogenesis; Photomovement; Blue Light Effects
Although these are separate, and sometimes subtle responses to light, each of the areas listed above is related to the others. Photomorphogenic studies concern the responses of organ-isms, at all levels, to light stimuli. This includes developmental changes, structural adaptations, pigment dispersion and concentration, and growth responses (Kendrick and Kronenberg, 1994;


Table 14. Circadian Rhythms

1935	day-night leaf movement rhythm associated with photoperiodic timing	Bunning
1940	light is the primary synchronizer in daily rhythms	Kalmus...
1954	temperature independence of daily rhythms portends a functional biological clock	Pittendrigh
1958-1960	phase response and action spectrum for resetting the clock by light	Hastings
1969	the pineal as a transplantable oscillator in birds	Menaker
1971	clock mutants in Drosophila: the period gene	Konopka, Benzer
1972	suprachiasmatic nucleus; the central oscillator in mammals	Moore, Zucker
1973	clock mutants in neurospora: the frequency gene	Feldman
1985-1995	cloning of Drosophila, neurospora, and synechococcus clock genes; light entrainment of molecular oscillations, feedback model	Hall, Rosbash, Young, Dunlap, Loros
1992	suprachiasmatic nucleus transplantation to mammalian host carries phase and period	Menaker
1995-1999	clock mutants in mice, characterization of clock genes and proteins	Takahashi, Reppert, Schwartz

Table 15. Photomorphogenesis

1940-1960	response of plants to red/far-red light	Bothwick, Hendricks, Hillman, Klein, Toole, Withrows
1960-1970	high irradiance responses of plants	Siegelman, Mohr, Hartmann, Mancinelli, Schafer
	purification characterization of phytochrome as the red/far-red reversible photoreceptor	Siegelman, Butler, Briggs, Furuya, Schafer
	chloroplast movements mediated by phytocrome; polarotropism	Haupt
1960-1980	action of phytochrome in photomorphogenesis	Mohr, Quail
1970-1980	characterization and localization of phytochromes	Pratt, Furuya
1980	light quality and shade avoidance quantified, Pr-Pfr photoequilibrium	Smith
	chemical structure of phytochromobilin and its photoisomerization	Ruediger, Lagarias, Song
1980-1990	light-induced conformational changes in phytochromes	Pratt, Lagarias, Braslavsky, Schaffner, Song
1985	phytochrome gene family identified	Quail, Pratt
	and their functional specificities elucidated	Furuya, Quail, Whitelam
1990	phytochrome established as a light switch for circadian rhythms	Kay
	molecular mechanisms of phytochrome-mediated light signal transduction	Song, Chua, Neuhaus, Quail, Chory, Choi, Song, Nagatami, Schafer, Nagy
1997	bacteriophytochromes discovered in cyanobacteria, and other prokaryotes	Lamparter, Vierstra

Table 16. Photomovement

1906	photomovement of ciliate, Stentor coeruleus	Jenning
1960s	phototaxis of Eeuglena gracilis	Diehn, Lenci, Nultsch
1970	phototropism of phycomyces characterized	Lipson, Delbrueck
1979	photophobic and phototactic responses of ciliates characterized	Haeder, Poff, Song, Lenci, Matsuoka
1983-1993	rhodopsin-like photoreceptors proposed for phototaxis of Chlamydomonas reinhardtii	Foster, Nakanishi, Hegernan
1990	chemical structures of the photoreceptor stentorin	Song
	and blepharismin	Song, Lenci, Matsuoka

Table 17. Phototropism and Blue Light Effects

1950s	phototropic curvature and auxin translocation related	Briggs
1960s	action spectra for phototropism	Thieman, Shropshire, Poff
	flavin proposed as the phototropic receptor	Galston
1993	Cryl identified as flavin-containing blue light receptor for hypocotyl elongation	Cashmore
1990	phototropin identified as flavin-containing light receptor for phototropism; and blue light-activateable autophosphorylating kinase	Briggs

Quail, et al., 1995; Wells, et al., 1996; Smith, 2000). Smith (1977) describes the light signals that elicit the metabolic changes required for these responses as "a switching mechanism." Photomovement is a light-mediated change in the configuration of an organism, sometimes including a pattern of growth toward or away from the stimulus (Song, 1983; Spudich, 1991). It includes phototropism, the bending of a growing stem toward light; phototaxis, a movement response in motile organisms; and photokinesis, an increase in response due to an increase in the intensity of the stimulation. Some of these photoresponses (e.g., phototropism and phototaxis) are triggered by wavelengths in the blue region of the spectrum and are called "blue-light effects" (Ahmad and Cashmore, 1996; Briggs and Liscum, 1997). Photomorphogenesis in some fungi is exclusively mediated by a blue photoreceptive pigment. Tables 15, 16 and 17 list this century's advances in each of these areas.

Organization
Of central importance to the development of any field is organization (Daniels, 1997). It helps to focus research, allow for cross-fertilization, educates both the scientific community and the public about an area of research, provides visibility and, with a nod to viability, may help in securing government funds. The quadrennial meetings of the IUPB stem from the efforts of a group of European scientists who met in a French bistro over 60 years ago (Latarjet, 1997). And in what may be termed progress (or at least wordsmanship), the group again changed its name in 2000.


Table 18. Organization

1928-1951	Comite International de la Lumiere (CIL)	Saidman, Reyn, Friedrich, Morikofer
1951-1976	Comite International de Photobiologie (CIP)	Morikofer, Rajewski, Blum, Hollaender, Meyer, Latarjet
1976-2000	Association Internationale de Photobiologie (AIP)
2000	International Union for Photobiology (IUPB)

So far the CIP-AIP-IUPB has held 14 world congresses on photobiology.

Table 19. World Congresses

Number	Year	Location	President	Secretary-General
I	1954	Amsterdam, Holland	Ebbenhorst-Tengbergen, J.W.	Voogd, J.
II	1957	Turin, Italy	Ponzio, M.	Mathi, G. and Benass, E.
III	1960	Copenhagen, Denmark	Christensen, B., Chr.	Buchman B.
IV	1964	Oxford, UK	Bowen, E.J.	Millot, N. and Vince-Prue, D.
V	1968	Dartmouth, USA	Setlow, R.B.	Gordon, S.
VI	1972	Bochum, Germany	Schenck, G.0.	Tronnier, H.
VII	1976	Rome, Italy	Pocchiari, F.	Castellani, A.
VIII	1980	Strasbourg, France	Helene, C.	Charlier, M.
IX	1984	Philadelphia, USA	McElroy, W. D.	Longworth, J. W.
X	1988	Jerusalem, Israel	Riklis, E.	Avron, M., Malhin, S. and Ottolenghi, M.
XI	1992	Kyoto, Japan	Takebe, H.	Ikenaga, M.
XII	1996	Vienna, Austria	Hönigsmann, H.	Dubbelman, T.
XIII	2000	San Francisco, USA	Gasparro, F.	Oleinick, N.
XIV	2004	Jeju, Korea	Song, P-S	Hahn, T-R
XV	2009	Düsseldorf, Germany	Krutmann, J. Organizer

One scientist who helped greatly in the organization of photobiologists in Europe (especially Britain) was Edna Roe. For her efforts she is recognized at each international meeting by a special lecture.


Table 20. Edna Roe Lectures 1976-2004

1976	Paterson	Canada
1980	Kripke	USA
1984	Sutherland	USA
1988	Moustacchi	France
1992	Völker	Netherlands
1996	Chory	USA
2000	Barry	USA
2004	Bornman	Denmark

Concurrently, the San Francisco meeting (2000) was the 28th one for the American Society for Photobiology, an organization almost single handedly started by Smith in 1972 (Smith, 1997). His efforts produced a viable group of photobiologists and may have been the impetus for the beginnings of similar groups in other countries. Indeed, it is easier to identify oneself as a photobiologist if you can point to a society by that name and publish in the journals that spring from those associations.

Left Outs
I will not have to remind the reader that much of the field Photobiology has not been highlighted in this brief review. There are many additional books and review articles that detail the progress of Photobiology. Some of these can be found in the reference pages of the nine articles contained in the symposium "Landmarks in Photobiology" edited by Urbach (1997). Others are cited in the chapters of this and other books and journals.

A Note About the Reference List
It is not uncommon for reference lists in review articles that cover just a portion of any one area of Photobiology to run into the hundreds. I have made no attempt to construct the much longer list that would be necessary for this general historical chapter. Rather, I recommend you to the lists contained in the limited number of reviews I do cite. Also, with some exceptions, I have not cited the original reference for a result but, rather, a review that contains that reference. This allowed for an abbreviated list.

A Note About the Tables
To keep the lists of references to a manageable number, I made no attempt to identify most of the seminal manuscripts associated with the long list of authors.

Acknowledgements - Many photobiologists contributed to this review. The following made detailed recommendations; Brainard, Dougherty, Hastings, Hönigsmann, Jagger, Loach, Noonan, Song, Spikes, Urbach, Valenzeno.

This article was originally excerpted with permission from:
Photobiology for the 21st Century
Thomas P. Coohill and Dennis P. Valenzeno, editors
Valdenmar Publishing Company. Overland Park, Kansas, 2001
and further revised in April 2008

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