Melanins and their possible roles through biological evolution

Melanins are biopolymers which structures can be very simple or very complex. From a single essential amino acid, phenylalanine, to fully mature melanosomes, a series of events takes place: melanogenesis. A part of haemoglobin, melanins are the only pigment endogenously synthesised in humans. Their synthesis takes place in the melanocyte, a cell from neurectodermal origin (neural crest, neural tube, melanoblasts). Two important functions have been attributed to melanin: optical efficiency of the eye and colour pattern, but their role might have been much larger in lower vertebrates and several micro-organisms. By their structure, melanins have very original biophysical bioproperties. They could act as intrinsic semiconductors and may de-excite certain biological molecules by converting electronic energy into heat. Being themselves free radicals, they certainly play a major role in the quenching of free radicals produced by ultraviolet radiation. In their granular or particular form, they absorb or reflect the non-ionising radiations. Furthermore, like weak cation exchange polymers, eumelanins have the capacity to bind substantial amount of metal ions or drugs. Phaeomelanins, sulphur containing low molecular weight, may have controlled the redox state of the early steps of life on earth.

In human, the skin protection role attributed to melanins is controversial. If melanins have played a major role in the establishment of a North South gradient of skin colour, it is by no mean, an adaptation phenomenon for the darker population living under strong sun exposures.     

Chemical evolution and the origin of life.

During the last three decades major advances have been made in our understanding of the formation of carbon compounds in the universe and of the occurence of processes of chemical evolution. 1) Carbon and other biogenic elements (C,H,N,O,S and P) are some of the most abundant in the universe. 2) The interstellar medium has been found to contain a diversity of molecules of these elements. 3) Some of these molecules have also been found in comets which are considered the most primordial bodies of the solar system. 4) The atmospheres of the outer planets and their satellites, for example, Titan, are actively involved in the formation of organic compounds which are the precursors of biochemical molecules. 5) Some of these biochemical molecules, such as amino acids, purines and pyrimidines, have been found in carbonaceous chondrites. 6) Laboratory experiments have shown that most of the monomers and oligomers necessary for life can be synthesized under hypothesized but plausible primitive Earth conditions from compounds found in the above cosmic bodies. 7) It appears that the primitive Earth had the necessary and sufficient conditions to allow the chemical synthesis of biomacromolecules and to permit the processes required for the emergence of life on our planet. 8) It is unlikely that the emergence of life occurred in any other body of the solar system, although the examination of the Jovian satellite Europa may provide important clues about the constraints of this evolutionary process. Some of the fundamental principles of chemical evolution are briefly discussed.     

Chemical evolution on the giant planets and Titan

We summarize the current status of atmospheric chemistry in the atmospheres of the outer solar system with special emphasis on the question of HCN formation on Jupiter, differences between polar and equatorial compositions on Jupiter, the coloration of the Great Red Spot, and the unique environment of Titan.     

Production and evolution of carbonaceous material by ion irradiation in space.

We review recent experimental studies concerning the evolution, driven by ion irradiation, of carbonaceous material from frozen gas to a refractory molecular solid. Under further irradiation the latter changes to a polymer-like material and ultimately to amorphous carbon. Most of the results have been obtained by "in situ" and remote IR and Raman spectroscopy. The results have been applied to demonstrate that molecular solids may be easily formed by irradiation of frozen mantles in dense interstellar clouds. Polymer-like material and amorphous carbons may result by further irradiation of organic mantles on grains in the diffuse interstellar medium. Those grains, during the aggregation to form extended bodies like comets (T-Tau phase of the Sun), are further modified. These latter are also irradiated, after the comet formation, during their long stay in the Oort cloud. In particular it has been suggested that comet may develop an ion-produced cometary organic crust that laboratory evidences show to be stable against temperature increases experienced during passages near the Sun. The comparison between the Raman spectra of some IDP (Interplanetary Dust Particles) and the Raman spectra of some ion-produced amorphous carbons, is also discussed.     

Large-size space laboratory for biological orbit experiments.

The study of space factors on living systems has great interest and long-term experiments during orbital flight will be important tool for increasing our knowledge. Realization of such experiments is limited by constraints of modern space stations. A new technology of large-size space laboratory for biological experiments has been developed on the basis of polymerization techniques. Using this technique there are no limits of form and size of laboratory for a space station that will permit long term experiments on Earth orbit with plants and animals in sufficient volume for creation of closed self-regulating ecological systems. The technology is based on experiments of the behavior of polymer materials in simulated free space conditions during the reaction of polymerization. The influences of space vacuum, sharp temperature changes and space plasma generated by galactic rays and Sun irradiation on chemical reaction were evaluated in their impact on liquid organic materials in laboratory conditions. The results of our study shows, that the chemical reaction is sensitive to such space factors. But we believe that the technology of polymerization could be used for the creation of space biological laboratories in Earth orbit in the near future.     

Chemical evolution in space--a source of prebiotic molecules.

In Laboratory Astrophysics at Leiden University a laboratory analog for following the chemical evolution of interstellar dust in space shows that the dust contains the bulk of organic material in the universe. We follow the photoprocessing of low temperature (10 K) mixtures of ices subjected to vacuum ultraviolet radiation in simulation of interstellar conditions. The most important, but necessary, difference is in the time scales for photo-processing. One hour in the laboratory is equivalent to one thousand years in low density regions of space and as much as, or greater than, ten thousand to one million years in the depths of dense molecular clouds. The ultimate product of photoprocessing of grain material in the laboratory is a complex nonvolatile residue which is yellow in color and soluble in water and methanol. The molecular weight is greater than the mid-hundreds. The infrared absorption spectra indicate the presence of carboxylic acid and amino groups resembling those of other molecules of presumably prebiological significance produced by more classical methods. One of our residues, when subjected to high resolution mass spectroscopy gave a mass of 82 corresponding to C4H6H2 after release of CO2 and trace ammounts of urea suggesting amino pyroline rings. The deposit of prebiotic dust molecules occurred as many as 5 times in the first 500-700 million years on a primitive Earth by accretion during the passage of the solar system through a dense interstellar cloud. The deposition rate during each passage is estimated to be between 10(9) and 10(10) g per year during the million or so years of each passage; i.e., a total deposition of 1O(9)-10(10) metric tons of complex organic material per passage.     

Chemical evolution of primitive solar system bodies.

In this paper we summarize some of the most salient observations made recently on the organic molecules and other compounds of the biogenic elements present in the interstellar medium and in the primitive bodies of the solar system. They include the discovery of the first phosphorus molecular species in dense interstellar clouds, the presence of complex organic ions in the dust and gas phase of Halley's coma, the finding of unusual, probably presolar, deuterium-hydrogen ratios in the amino acids of carbonaceous chondrites, and new developments on the chemical evolution of Titan, the primitive Earth, and early Mars. Some of the outstanding problems concerning the synthesis of organic molecules on different cosmic bodies are also discussed from an exobiological perspective.     

Arthropod model systems for studying complex biological processes in the space environment.

Three arthropod systems are discussed in relation to their complementary and potential use in Space Biology. In a next biosatellite flight, Drosophila melanogaster pre-adapted during several months to different g levels will be flown in an automatic device that separates parental from first and second generations. In the same flight, flies will be exposed to microgravity conditions in an automatic unit in which fly motility can be recorded. In the International Microgravity Laboratory-2, several groups of Drosophila embryos will be grown in Space and the motility of a male fly population will be video-recorded. In the Biopan, an ESA exobiology facility that can be flown attached to the exterior of a Russian biosatellite, Artemia dormant gastrulae will be exposed to the space environment in the exterior of the satellite under a normal atmosphere or in the void. Gastrulae will be separated in hit and non-hit populations. The developmental and aging response of these animals will be studied upon recovery. With these experiments we will be able to establish whether exposure to the space environment influences arthropod development and aging, and elaborate on some of the cellular mechanisms involved which should be tested in future experiments.     

Optimal trajectory planning of free-floating space manipulator using differential evolution algorithm

The existence of the path dependent dynamic singularities limits the volume of available workspace of free-floating space robot and induces enormous joint velocities when such singularities are met. In order to overcome this demerit, this paper presents an optimal joint trajectory planning method using forward kinematics equations of free-floating space robot, while joint motion laws are delineated with application of the concept of reaction null-space. Bézier curve, in conjunction with the null-space column vectors, are applied to describe the joint trajectories. Considering the forward kinematics equations of the free-floating space robot, the trajectory planning issue is consequently transferred to an optimization issue while the control points to construct the Bézier curve are the design variables. A constrained differential evolution (DE) scheme with premature handling strategy is implemented to find the optimal solution of the design variables while specific objectives and imposed constraints are satisfied. Differ from traditional methods, we synthesize null-space and specialized curve to provide a novel viewpoint for trajectory planning of free-floating space robot. Simulation results are presented for trajectory planning of 7 degree-of-freedom (DOF) kinematically redundant manipulator mounted on a free-floating spacecraft and demonstrate the feasibility and effectiveness of the proposed method.     

Capacity building in space law and space policy

A high level of expertise in space policy and law is required to initiate and keep pace with the expansion of space activities, including those undertaken by the private space industry. Space activities generally refer to those undertakings that are carried out with the use of several technologies for the exploration and utilization of outer space often for scientific, military, economic and social proposes within international and national policy and regulatory frameworks. Space policies and legal regimes determine the scope, nature, pace, possibility and development of space undertakings. Therefore, appropriate space policies and regulatory regimes, both at the international and national levels, are indispensable for the initiation, operation and enhancement of space activities. There are various regulatory models and approaches for regulating space activities, and for building capacity in space law and space policy. It is imperative to have the appropriate human resources and capabilities in the development and implementation of space policies and space legal regimes. This crucial requirement has been well recognized in the more advanced space-faring nations, but not to the same level in other space-faring or space-aspiring nations.     

Insects as test systems for assessing the potential role of microgravity in biological development and evolution.

Gravity and radiation are undoubtedly the two major environmental factors altered in space. Gravity is a weak force, which creates a permanent potential field acting on the mass of biological systems and their cellular components, strongly reduced in space flights. Developmental systems, particularly at very early stages, provide the larger cellular compartments known, where the effects of alterations in the size of the gravity vector on living organisms can be more effectively tested. The insects, one of the more highly evolved classes of animals in which early development occurs in a syncytial embryo, are systems particularly well suited to test these effects and the specific developmental mechanisms affected. Furthermore, they share some basic features such as small size, short life cycles, relatively high radio-resistance, etc. and show a diversity of developmental strategies and tempos advantageous in experiments of this type in space. Drosophila melanogaster, the current biological paradigm to study development, with so much genetic and evolutionary background available, is clearly the reference organism for these studies. The current evidence on the effects of the physical parameters altered in space flights on insect development indicate a surprising correlation between effects seen on the fast developing and relatively small Drosophila embryo and the more slowly developing and large Carausius morosus system. In relation to the issue of the importance of developmental and environmental constraints in biological evolution, still the missing link in current evolutionary thinking, insects and space facilities for long-term experiments could provide useful experimental settings where to critically assess how development and evolution may be interconnected. Finally, it has to be pointed out that since there are experimental data indicating a possible synergism between microgravity and space radiation, possible effects of space radiation should be taken into account in the planning and evaluation of experiments designed to test the potential role of microgravity on biological developmental and evolution.     

Creation of biological module for self-regulating ecological system by the way of polymerization of composite materials in free space.

The large-size frame of space ship and space station can be created with the use of the technology of the polymerization of fiber-filled composites and a liquid reactionable matrix applied in free space or on the other space body when the space ship or space station will be used during a long period of time. For the polymerization of the station frame the fabric impregnated with a long-life polymer matrix (prepreg) is prepared in terrestrial conditions and, after folding, can be shipped in a compact container to orbit and kept folded on board the station. In due time the prepreg is carried out into free space and unfolded. Then a reaction of matrix polymerization starts. After reaction of polymerization the durable frame is ready for exploitation. After that, the frame can be filled out with air, the apparatus and life support systems. The technology can be used for creation of biological frame as element of self regulating ecological system, and for creation of technological frame which can be used for a production of new materials on Earth orbit in microgravity conditions and on other space bodies (Mars, Moon, asteroids) for unique high price mineral extraction. Based on such technology a future space base on Earth orbit with volume of 10(6) m3 and a crew of 100 astronauts is considered.     

Fullerenes in space.

The discovery and synthesis of fullerenes led to the hypothesis that they may be present and stable in interstellar space. Fullerenes have been reported in an impact crater on the LDEF spacecraft. Investigations of fullerenes in carbonaceous meteorites have yielded only small upper limits. Fullerene compounds and their ions could be interesting carrier molecules for some of the "diffuse interstellar bands" (DIBs), a long standing mystery in astronomy. We have detected two new diffuse bands that are consistent with laboratory measurements of the C60+, as first evidence for the largest molecule ever detected in space. Criteria for this identification are discussed. The inferred abundance (up to 0.9 % of cosmic carbon locked in C60+) suggests that fullerenes may play an important role in interstellar chemistry. We present new observations on DIB substructures consistent with fullerene compounds, and the search for neutral C60 in the diffuse medium.     

从时空里归来

1979年,我被外派到巴拿马籍的荒原日出号工作,同时被外派的还有1名木匠、4名水手和1名服务员.船队中还有来自意大利的高级船员、菲律宾和印度的技工等,是多国船员组成的船队.     

Pleurodeles waltl, amphibian, Urodele, is a suitable biological model for embryological and physiological space experiments on a vertebrate.

Pleurodeles waltl (amphibian, Urodele) is an appropriate biological model for space experiments on a vertebrate. One reason for interest in this animal concerns the study of the effects of absence of gravity on embryonic development. First, after mating (on Earth) the females retain live, functional sperm in their cloacum for up to 5 months, allowing normal in vivo fertilisation after hormonal stimulation. Second, their development is slow, which allows analyses of all the key stages of ontogenesis from the oocyte to swimming tailbud embryos or larvae. We have performed detailed studies and analyses of the effects of weightlessness on amphibian Pleurodeles embryos, fertilised and allowed to develop until the swimming larvae stage. These experiments were performed in space during three missions on the MIR-station: FERTILE I, FERTILE II and NEUROGENESIS respectively in 1996, 1998 and 1999. We show that in microgravity abnormalities appeared at specific stages of development compared to 1g-centrifuge control embryos and 1g-ground control embryos. In this report we describe abnormalities occurring in the central nervous system. These modifications occur during the neurulation process (delay in the closure of the neural tube and failure of closure of this tube in the cephalic area) and at the early tailbud stage (microcephaly observed in 40% of the microgravity-embryos). However, if acephalic and microcephalic embryos are not taken into account, these abnormalities did not disturb further morphological, biochemical and functional development and the embryos were able to regulate and a majority of normal hatching and swimming larvae were obtained in weightlessness with a developmental time-course equivalent to that of 1g-centrifuge control embryos (on the MIR station) and 1g-ground control embryos.     

The role of the space industry in building capacity in emerging space nations

The space industry in established space-faring nations is playing an increasingly important role in the development of capacity in emerging space nations. The role of industry ranges from provision of turn-key systems, to provision of training and joint development of satellites in partnership with emerging space countries. Ranked number 1 worldwide in terms of satellites ordered in 2006, Thales Alenia Space is at the heart of the most high performance satellite technologies in both civil and defense sectors. The company has been involved in parterships with a number of emerging space nations. This paper discusses several key factors for successful interaction of industry with national space programmes in emerging space nations.     

Crickets in space: morphological, physiological and behavioral alterations induced by space flight and hypergravity.

"Crickets in Space" was a Neurolab experiment by which the balance between genetic programs and the gravitational environment for the development of a gravity sensitive neuronal system was studied. The model character of crickets was justified by their external gravity receptors, identified position-sensitive interneurons (PSI) and gravity-related compensatory head response, and by the specific relation of this behavior to neuronal arousal systems activated by locomotion. These advantages allowed to study the impact of modified gravity on cellular processes in a complex organism. Eggs, 1st, 4th and 6th stage larvae of Acheta domesticus were used. Post-flight experiments revealed a low susceptibility of the behavior to micro- and hypergravity while the physiology of the PSI was significantly affected. Immunocytological investigations revealed a stage-dependent sensitivity of thoracic GABAergic motoneurons to 3 g-conditions concerning their soma sizes but not their topographical arrangement. The morphology of neuromuscular junctions was not affected by 3 g-hypergravity. Peptidergic neurons from cerebral sensorimotor centers revealed no significant modifications by microgravity (micro g). The contrary physiological and behavioral results indicate a facilitation of 1 g-readaptation originating from accessory gravity, proprioceptive and visual sense organs. Absence of anatomical modifications point to an effective time window of micro g or 3 g-expo-sure related to the period of neuronal proliferation. The analysis of basic mechanisms of how animals and man adapt to altered gravitational conditions will profit from a continuation of the project "Crickets in Space".     

Satellite orbits in Levi-Civita space

In this paper we consider satellite orbits in central force field with quadratic drag using two formalisms. The first using polar coordinates in which the satellite angular momentum plays a dominant role. The second is in Levi-Civita coordinates in which the energy plays a central role. We then merge these two formalisms by introducing polar coordinates in Levi-Civita space and derive a new equation for satellite orbits which unifies these two paradigms. In this equation energy and angular momentum appear on equal footing and thus characterize the orbit by its two invariants. Using this formalism we show that equatorial orbits around oblate spheroids can be expressed analytically in terms of Elliptic functions. In the second part of the paper we derive in Levi-Civita coordinates a linearized equation for the relative motion of two spacecrafts whose trajectories are in the same plane. We carry out also a numerical verification of these equations.