The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Shigeyoshi Osaki - One of the best experts on this subject based on the ideXlab platform.
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The effects of seasonal changes on the molecular weight of Nephila clavata spider silk
Polymer Journal, 2016Co-Authors: Shigeyoshi Osaki, Keizo Yamamoto, Takashi Matsuhira, Hiromi SakaiAbstract:The molecular weight of spider proteins contained in the major ampullate glands of spiders collected during different periods. The standard deviation is also indicated. A peak for molecular weight is observed in mid-autumn, which corresponds to the mating season. Silk proteins were taken from the major ampullate glands found in the abdomens of Nephila clavata spiders that were collected on different days during an autumn season in Japan. The molecular weights of the silk proteins taken from 125 spiders were determined under a reduced state using electrophoresis. It was found that the molecular weight of N. clavata spider silk protein changed depending on the time period during the autumn season and showed a peak value of ~300 kDa during mating season. However, the molecular weight of N. clavata spider silk protein was, on average, ~270 kDa except during mating season. Such a peak in the molecular weight for female N. clavata may be ascribed to the necessity for building mechanically strong orb-webs, which consist of silk with relatively large proteins for the purpose of accepting many male spiders.
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The effects of seasonal changes on the molecular weight of Nephila clavata spider silk
Polymer Journal, 2016Co-Authors: Shigeyoshi Osaki, Keizo Yamamoto, Takashi Matsuhira, Hiromi SakaiAbstract:The molecular weight of spider proteins contained in the major ampullate glands of spiders collected during different periods. The standard deviation is also indicated. A peak for molecular weight is observed in mid-autumn, which corresponds to the mating season.
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Molecular weight of Nephila clavata spider silk
Polymer Journal, 2015Co-Authors: Takashi Matsuhira, Shigeyoshi OsakiAbstract:Band patterns for N. clavata spider silk protein and for three different markers in 3% SDS-PAGE. M: marker, A: spider silk solution under a reduced state, B: spider silk solution under an unreduced state. The reduction due to a reductant cleaves the disulfide bonds and decreases the molecular weight from ca . 600 to ca . 270 kDa. Spider silk protein with ca . 600 kDa is suggested to be crosslinked by disulfide bonding between the two proteins. The molecular weight of Nephila clavata spider silk was determined to be ca. 600 kDa, under unreduced conditions, corresponding to its natural state, using the sodium dodecyl sulfate polyacrylamide gel electrophoresis method and a protein marker with a maximum molecular weight of 500 kDa. The addition of 2-mercaptoethanol into the spider silk solution decreased the molecular weight from ca. 600 kDa to ca. 270 kDa. Such a dramatic decrease in the molecular weight was ascribed to the presence of 2-mercaptoethanol as a reductant. This finding indicates the possibility that the reduction process cleaved the disulfide bonds formed between the spider silk proteins and then drastically decreased the molecular weight from ca. 600 to ca . 270 kDa. These results suggest that N. clavata spider silk proteins might consist of two proteins with a molecular weight of ca. 270 kDa that are crosslinked by disulfide bonds and exist as a dimer of ca. 600 kDa.
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Effects of UV irradiation on the molecular weight of spider silk
Polymer Journal, 2013Co-Authors: Takashi Matsuhira, Keizo Yamamoto, Shigeyoshi OsakiAbstract:The molecular weight of the Nephila clavata spider dragline was determined to be 272±14 kDa using a SDS-PAGE method. The effects of ultraviolet (UV) irradiation on the molecular weight of the spider dragline were studied and compared with that of silkworm silk. The band densities observed using SDS-PAGE for the spider dragline and silkworm silk decreased with the UV irradiation time, suggesting decomposition due to the cleavage of protein chain molecules. It was found that the rate constant of degradation due to UV irradiation for the silkworm silk was larger by 1.7 than that for the N. clavata spider dragline. This result indicates that the N. clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk. UV irradiation cleaves chemical bonds and decomposes the silk chains into fragments. The effects of UV irradiation on spider silk were studied from the viewpoint of the quantity of silk proteins. The ratio of the uncleaved quantity to the initial quantity for the spider silk and silkworm silk is plotted as a function of the UV irradiation time. The silkworm silk decomposes more easily than the spider silk. The result indicates that Nephila clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk.
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Effects of UV irradiation on the molecular weight of spider silk
Polymer Journal, 2013Co-Authors: Takashi Matsuhira, Keizo Yamamoto, Shigeyoshi OsakiAbstract:UV irradiation cleaves chemical bonds and decomposes the silk chains into fragments. The effects of UV irradiation on spider silk were studied from the viewpoint of the quantity of silk proteins. The ratio of the uncleaved quantity to the initial quantity for the spider silk and silkworm silk is plotted as a function of the UV irradiation time. The silkworm silk decomposes more easily than the spider silk. The result indicates that Nephila clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk.
Masaaki Miyashita - One of the best experts on this subject based on the ideXlab platform.
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Total synthesis of NPTX-5 and NPTX-6, Joro spider (Nephila clavata) toxins having a unique putreanine trimer and putreanine tetramer acylpolyamine chain
Tetrahedron Letters, 1998Co-Authors: Hiroaki Saito, Terumi Nakajima, Masahiro Miyazawa, Yasuhiro Itagaki, Etsuko Yuri, Masaaki MiyashitaAbstract:Abstract The first total synthesis of NPTX-5 and NPTX-6, Joro spider ( Nephila clavata ) toxins having a 4-hydroxyindole nucleus and a unique putreanine trimer and tetramer acylpolyamine chain, respectively, has been achieved by the iterative use of a key azide compound.
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Structures of spider toxins: hydroxyindole-3-acetylpolyamines and a new generalized structure of type-E compounds obtained from the venom of the Joro spider, Nephila clavata.
Toxicon : official journal of the International Society on Toxinology, 1998Co-Authors: Miki Hisada, Masaaki Miyashita, Hiroshi Irie, Yasuhiro Itagaki, Tsuyoshi Fujita, Hideo Naoki, Terumi NakajimaAbstract:Facile structure determination of acylpolyamines, glutamatergic nerve blocker obtained from the venom of the Joro spider (Nephila clavata) was carried out with the use of μ-column LC/MS and high energy collision induced dissociation (CID) mass spectrometry. 6-hydroxyindole-3-acetyl was proposed previously as a putative partial structure, for the acyl moiety of hydroxyindole-type polyamines (NPTX-1∼6). The NMR data obtained for NPTX-6, NPTX-687 and hydroxyindole-3-acetic acid which was released by acid hydrolysis of Nephila clavata crude venom extracts proved that the lipophilic head is the 4-hydroxyindole-3-acetic acid. Various hydroxyindole-3-acetyl polyamines were found in N. clavata venom and characterized by mass spectrometry. As a result, type-E, a new class of generalized acylpolyamine structure was proposed in addition to the previously reported polyamine backbones type-A to -D.
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Total synthesis of Nephilatoxin-1 (NPTX-1), a Joro spider (Nephila clavata) toxin having a 4-hydroxyindole nucleus
Tetrahedron Letters, 1997Co-Authors: Masaaki Miyashita, Masayuki Matsushita, Hiroaki Saito, Masahiro Miyazawa, Yasuhiro Itagaki, Terumi NakajimaAbstract:Abstract The first total synthesis of Nephilatoxin-1 (NPTX-1), a Joro spider ( Nephila clavata ) toxin having a 4-hydroxyindole nucleus, has been achieved by using two key azide intermediates.
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synthetic studies on Nephilatoxins new neurotoxins of joro spider Nephila clavata
Journal of Synthetic Organic Chemistry Japan, 1996Co-Authors: Masaaki MiyashitaAbstract:Synthetic studies on Nephilatoxins which has been carried out in the author's group is reviewed. Nephilatoxins (NPTX-112) isolated from Joro Spider (Nephila clavata) have been demonstrated to be potent blockers of glutaminergic neurotransmission as well as other spider toxins and are emerging as unique tools for understanding excitatory amino acid neurotransmission. In this report chemical synthesis of spider toxins involving synthetic strategy and total synthesis of NPTX-712 is described in which three azide intermediates were designed and employed as key compounds for construction of the characteristic polyamine chains of the toxins. In addition new results of biological activities obtained by using synthetic Nephilatoxins (NPTX-712) and their congeners incorporating a D-amino acid are also described.
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TOTAL SYNTHESIS OF NephilaTOXIN-7 (NPTX-7), A NEW NEUROTOXIN OF JORO SPIDER (Nephila clavata)
Tetrahedron Letters, 1995Co-Authors: Masayuki Matsushita, Takashi Toki, Hiroshi Irie, T. Kanemura, Susumi Hatakeyama, Masaaki MiyashitaAbstract:Abstract The first and highly efficient total synthesis of Nephilatoxin-7 (NPTX-7), a new neurotoxin of Joro spider ( Nephila clavata ), has been achieved by employing the azide strategy wherein the three characteristic polyamine components of the toxin, cadaverine and bis-putreanine, were efficiently constructed by the iterative use of key azide intermediates.
Terumi Nakajima - One of the best experts on this subject based on the ideXlab platform.
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Total synthesis of NPTX-5 and NPTX-6, Joro spider (Nephila clavata) toxins having a unique putreanine trimer and putreanine tetramer acylpolyamine chain
Tetrahedron Letters, 1998Co-Authors: Hiroaki Saito, Terumi Nakajima, Masahiro Miyazawa, Yasuhiro Itagaki, Etsuko Yuri, Masaaki MiyashitaAbstract:Abstract The first total synthesis of NPTX-5 and NPTX-6, Joro spider ( Nephila clavata ) toxins having a 4-hydroxyindole nucleus and a unique putreanine trimer and tetramer acylpolyamine chain, respectively, has been achieved by the iterative use of a key azide compound.
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Structures of spider toxins: hydroxyindole-3-acetylpolyamines and a new generalized structure of type-E compounds obtained from the venom of the Joro spider, Nephila clavata.
Toxicon : official journal of the International Society on Toxinology, 1998Co-Authors: Miki Hisada, Masaaki Miyashita, Hiroshi Irie, Yasuhiro Itagaki, Tsuyoshi Fujita, Hideo Naoki, Terumi NakajimaAbstract:Facile structure determination of acylpolyamines, glutamatergic nerve blocker obtained from the venom of the Joro spider (Nephila clavata) was carried out with the use of μ-column LC/MS and high energy collision induced dissociation (CID) mass spectrometry. 6-hydroxyindole-3-acetyl was proposed previously as a putative partial structure, for the acyl moiety of hydroxyindole-type polyamines (NPTX-1∼6). The NMR data obtained for NPTX-6, NPTX-687 and hydroxyindole-3-acetic acid which was released by acid hydrolysis of Nephila clavata crude venom extracts proved that the lipophilic head is the 4-hydroxyindole-3-acetic acid. Various hydroxyindole-3-acetyl polyamines were found in N. clavata venom and characterized by mass spectrometry. As a result, type-E, a new class of generalized acylpolyamine structure was proposed in addition to the previously reported polyamine backbones type-A to -D.
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Structural characterization of a new acylpolyaminetoxin from the venom of Brazilian garden spider Nephilengys cruentata
Toxicon : official journal of the International Society on Toxinology, 1998Co-Authors: Mario Sergio Palma, Tsuyoshi Fujita, Yasuhiro Itagaki, Hideo Naoki, Terumi NakajimaAbstract:Abstract The use of mass spectrometry, in which high-energy CID and charge remote fragmentation both of protonated and sodium-attached molecular ions was applied, afforded the structural elucidation of a new acylpolyaminetoxin with M w =801 Da from the venom of the Brazilian garden spider Nephilengys cruentata . In spite of having the same M w of the NPTX-2, previously described in the venom of the Joro spider Nephila clavata , neither toxins are isomers. In order to differentiate them by using the most usual nomenclature, the new toxin was named NPTX-801C and the NPTX-2 was renamed to NPTX-801E. Both toxins have as common structure the 4-hydroxyindole-3-acetyl-asparaginyl-cadaveryl moiety in their molecules and their structure may be represented in a simplified way: NPTX-801E is HO–indole–Asn–Cad–Pta–Orn–Arg and NPTX-801C is HO–indole–Asn–Cad–Gly–Put–Pta–Pta.
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Total synthesis of Nephilatoxin-1 (NPTX-1), a Joro spider (Nephila clavata) toxin having a 4-hydroxyindole nucleus
Tetrahedron Letters, 1997Co-Authors: Masaaki Miyashita, Masayuki Matsushita, Hiroaki Saito, Masahiro Miyazawa, Yasuhiro Itagaki, Terumi NakajimaAbstract:Abstract The first total synthesis of Nephilatoxin-1 (NPTX-1), a Joro spider ( Nephila clavata ) toxin having a 4-hydroxyindole nucleus, has been achieved by using two key azide intermediates.
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Total Synthesis of Nephilatoxin-8 (NPTX-8), a New Neurotoxin of Joro Spider (Nephila clavata)
Chemistry Letters, 1993Co-Authors: Masaaki Miyashita, Terumi Nakajima, Masayuki Matsushita, Hideaki Sato, Takashi Toki, Hiroshi IrieAbstract:The first synthesis of Nephilatoxin-8 (NPTX-8), a new neurotoxin of Joro spider (Nephila clavata), has been achieved by employing two key azide intermediates for the incorporation of the characteristic polyamines of the toxin, cadaverine and spermidine.
Tadashi Miyashita - One of the best experts on this subject based on the ideXlab platform.
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The effects of forest fragmentation on web spider communities in urban areas
Biological Conservation, 1998Co-Authors: Tadashi Miyashita, Akira Shinkai, Takafumi ChidaAbstract:Spiders are generalist arthropod predators living in all kinds of forests. Since food limitation appears to be widespread, this group may be influenced by forest fragmentation in various ways. We examined web spider communities in one continuous forest and 17 forest fragments surrounded by built-up areas in Yokohama and Tokyo, Japan. Smaller fragments had fewer species and lower density of individuals. For a given size fragment, those in Yokohama harbored more species than those in Tokyo, probably due to the lower degree of isolation from surrounding fragments in Yokohama. Large araneids were most sensitive to fragmentation in the sense of species loss, small araneids intermediate, and theridiids least sensitive. The body size of Nephila clavata, a common species in fragments, was smaller in smaller fragments. We propose that one important mechanism of species loss in web spiders is the lower abundance of large prey in small fragments.
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decreased web investment in sub tropical Nephila clavata tetragnathidae
Acta Arachnologica, 1998Co-Authors: Claire K Cartan, Tadashi MiyashitaAbstract:Webs of Nephila clavata living in Okinawa, a sub-tropical region of Japan, were found to be significantly smaller and to have less number of radii and spirals than those seen in temperate Tokyo. According to recent papers, a web is thought to get smaller when prey is abundant (Sherman 1994), or before molting and egg-laying (Higgins 1990), but none of these explain web reduction in Okinawa. We propose an alternative explanation: the necessity of the spider to adjust its life cycle to a sub-tropical climate.
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design and prey capture ability of webs of the spiders Nephila clavata and argiope bruennichii
Acta Arachnologica, 1995Co-Authors: Tadashi Miyashita, Akira ShinkaiAbstract:The relationship between design and prey capture ability of webs was examined in the two orb-weaving spiders Nephila clavata and Argiope bruennichii. We collected unstressed webs of both species by framing them with large paper mounts, and exposed them at the same microhabitat. Webs of Nephila tended to capture more prey than those of Argiope, due to the larger number of sticky threads. However, the proportion of relatively large prey (2-6mm) was greater in Argiope, probably due to the larger amount of adhesive material attached to the web silk. We conducted another experiment to assess the retention ability of webs for large prey (20-25mm) by putting it on the web. The amount of time the prey remained trapped in the web was similar between the species, though the variation was large. We consider that the web of Nephila functions to capture large prey as well as very small prey.
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Size-related mating and mate guarding in the orb-web spiderNephila clavata (Araneae, Araneidae)
Journal of Insect Behavior, 1994Co-Authors: Tadashi MiyashitaAbstract:The orb-web spider Nephila clavata satisfies three conditions for assortative mating proposed by Ridley ( The Explanation of Organic Diversity. The Comparative Method and Adaptations for Mating , Clarendon, Oxford, 1983); (1) a large male advantage in male-male competition, (2) a correlation between female size and fecundity, and (3) a long pairing duration. To test Ridley's hypothesis, size assortative mating and guarding were examined in the field. When data were pooled over time, assortative mating was found but this was due to temporal covariation of body sizes of males and receptive females. After controlling for the effect of time, size assortative guarding was not detected, although females guarded by males were larger than those not guarded in the early breeding season. Possible reasons for the absence of size assortative guarding were discussed.
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Male-male competition and mating success in the orb-web spider,Nephila clavata, with reference to temporal factors
Ecological Research, 1993Co-Authors: Tadashi MiyashitaAbstract:Seasonal occurrence patterns of adults of both sexes, intensity of male-male interactions, and mating success in the spider, Nephila clavata , were examined in the field. Adult males began to attend female webs about 2 weeks before female maturation. Large adult males were abundant in the early breeding season, but small males increased later in the season. From the distribution of males among female webs and size relationship of males within a web, male-male interactions seemed to be more intense when most females were still subadult. This was verified by a field experiment in which males were artificially introduced to female webs that were attended by other males. It was found that the probability of introduced males remaining on subadult female webs was lower than that on adult webs. As mating occurred mostly in the period shortly after the female final molt and first male sperm precedence was known in all spiders reported so far, intense male-male competition on subadult female webs seemed to be reasonable. Male longevity had an important influence on the mating success of males with just-molted females. Mating success was also affected by the relative body size of males present in a given period. Since larger males occupied the position closest to females within a web and stayed there longer, relative body size appeared to influence mating success through male-male competition. Female body size at maturation declined with time; hence, males that attained sexual maturity earlier had the advantage of mating with larger and more fecund females. Therefore, early maturation as well as larger size seem to be two important trairs influencing the reproductive success of males.
Takashi Matsuhira - One of the best experts on this subject based on the ideXlab platform.
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The effects of seasonal changes on the molecular weight of Nephila clavata spider silk
Polymer Journal, 2016Co-Authors: Shigeyoshi Osaki, Keizo Yamamoto, Takashi Matsuhira, Hiromi SakaiAbstract:The molecular weight of spider proteins contained in the major ampullate glands of spiders collected during different periods. The standard deviation is also indicated. A peak for molecular weight is observed in mid-autumn, which corresponds to the mating season. Silk proteins were taken from the major ampullate glands found in the abdomens of Nephila clavata spiders that were collected on different days during an autumn season in Japan. The molecular weights of the silk proteins taken from 125 spiders were determined under a reduced state using electrophoresis. It was found that the molecular weight of N. clavata spider silk protein changed depending on the time period during the autumn season and showed a peak value of ~300 kDa during mating season. However, the molecular weight of N. clavata spider silk protein was, on average, ~270 kDa except during mating season. Such a peak in the molecular weight for female N. clavata may be ascribed to the necessity for building mechanically strong orb-webs, which consist of silk with relatively large proteins for the purpose of accepting many male spiders.
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The effects of seasonal changes on the molecular weight of Nephila clavata spider silk
Polymer Journal, 2016Co-Authors: Shigeyoshi Osaki, Keizo Yamamoto, Takashi Matsuhira, Hiromi SakaiAbstract:The molecular weight of spider proteins contained in the major ampullate glands of spiders collected during different periods. The standard deviation is also indicated. A peak for molecular weight is observed in mid-autumn, which corresponds to the mating season.
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Molecular weight of Nephila clavata spider silk
Polymer Journal, 2015Co-Authors: Takashi Matsuhira, Shigeyoshi OsakiAbstract:Band patterns for N. clavata spider silk protein and for three different markers in 3% SDS-PAGE. M: marker, A: spider silk solution under a reduced state, B: spider silk solution under an unreduced state. The reduction due to a reductant cleaves the disulfide bonds and decreases the molecular weight from ca . 600 to ca . 270 kDa. Spider silk protein with ca . 600 kDa is suggested to be crosslinked by disulfide bonding between the two proteins. The molecular weight of Nephila clavata spider silk was determined to be ca. 600 kDa, under unreduced conditions, corresponding to its natural state, using the sodium dodecyl sulfate polyacrylamide gel electrophoresis method and a protein marker with a maximum molecular weight of 500 kDa. The addition of 2-mercaptoethanol into the spider silk solution decreased the molecular weight from ca. 600 kDa to ca. 270 kDa. Such a dramatic decrease in the molecular weight was ascribed to the presence of 2-mercaptoethanol as a reductant. This finding indicates the possibility that the reduction process cleaved the disulfide bonds formed between the spider silk proteins and then drastically decreased the molecular weight from ca. 600 to ca . 270 kDa. These results suggest that N. clavata spider silk proteins might consist of two proteins with a molecular weight of ca. 270 kDa that are crosslinked by disulfide bonds and exist as a dimer of ca. 600 kDa.
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Effects of UV irradiation on the molecular weight of spider silk
Polymer Journal, 2013Co-Authors: Takashi Matsuhira, Keizo Yamamoto, Shigeyoshi OsakiAbstract:The molecular weight of the Nephila clavata spider dragline was determined to be 272±14 kDa using a SDS-PAGE method. The effects of ultraviolet (UV) irradiation on the molecular weight of the spider dragline were studied and compared with that of silkworm silk. The band densities observed using SDS-PAGE for the spider dragline and silkworm silk decreased with the UV irradiation time, suggesting decomposition due to the cleavage of protein chain molecules. It was found that the rate constant of degradation due to UV irradiation for the silkworm silk was larger by 1.7 than that for the N. clavata spider dragline. This result indicates that the N. clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk. UV irradiation cleaves chemical bonds and decomposes the silk chains into fragments. The effects of UV irradiation on spider silk were studied from the viewpoint of the quantity of silk proteins. The ratio of the uncleaved quantity to the initial quantity for the spider silk and silkworm silk is plotted as a function of the UV irradiation time. The silkworm silk decomposes more easily than the spider silk. The result indicates that Nephila clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk.
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Effects of UV irradiation on the molecular weight of spider silk
Polymer Journal, 2013Co-Authors: Takashi Matsuhira, Keizo Yamamoto, Shigeyoshi OsakiAbstract:UV irradiation cleaves chemical bonds and decomposes the silk chains into fragments. The effects of UV irradiation on spider silk were studied from the viewpoint of the quantity of silk proteins. The ratio of the uncleaved quantity to the initial quantity for the spider silk and silkworm silk is plotted as a function of the UV irradiation time. The silkworm silk decomposes more easily than the spider silk. The result indicates that Nephila clavata spider dragline was 1.7 times more resistant to UV irradiation than silkworm silk.