فهرست مطالب

  • Volume:1 Issue: 11, 2013
  • تاریخ انتشار: 1392/08/10
  • تعداد عناوین: 28
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  • Morad Shaban * Pages 1296-1301
    Seed deterioration is loss of seed quality, viability and vigor due to effect of adverse environmental factors. Many of our crops are reproduced through seeds, and throughout the world large quantities are produced, stored and transported. Seed ageing during storage may cause retardation of field establishment, and may eventually result in seedling abnormalities or even failure of emergence. During storage in gene banks, seed ageing may result in loss of genetic diversity. Extending and predicting the longevity of stored seeds is therefore highly relevant from a biodiversity as well as from an economic and social point of view. Seed rich in lipids has limited longevity due to its specific chemical composition. During storage of oily species declining trend of total oil content and seed germination can be observed. A fatty acid composition is the most important factor which determines oils susceptibility to oxidation Regardless of the problems which can be encountered due to the lack of space with favourable conditions, one must always keep in mind that seed is a living organism in which many biological processes, which can damage the seed and reduce its quality, take place, especially when the oily seed is in question
    Keywords: Aging, Seed
  • Hamze Esalat Nejad, Ahmad Esalat Nejad Pages 1302-1308

    Cochineal is the name of both crimson or carmine dye and the cochineal insect (Dactylopius coccus), a scale insect from which the dye is derived. There are other species in the genus Dactylopius which can be used to produce cochineal extract, but they are extremely difficult to distinguish from D. coccus, even for expert taxonomists, and the latter scientific name (and the use of the term "cochineal insect") is therefore commonly used when one is actually referring to other biological species. D. coccus itself is native to tropical and subtropical South America and Mexico. This insect lives on cacti from the genus Opuntia, feeding on moisture and nutrients in the cacti. The insect produces carminic acid which deters predation by other insects. Carminic acid can be extracted from the insect's body and eggs to make the dye. Cochineal is primarily used as a food coloring and for cosmetics

    Keywords: Cochineal, Dyeing, Dactylopius coccus, wool, Carpet
  • Morad Shaban * Pages 1309-1314
    This study was performed in order to evaluate the effects of irrigation and application of Zn fertilizer on  seed storage proteins  in chickpea, Azad cultivar. Experiment was performed in an factorial using randomized complete block design with three replications. In this experiment, two factor consist of irrigation in three levels (I1= non irrigation and I2= irrigation in flowering stage), Zn fertilizer in six levels (Zn1=0, Zn2=15kg/ha, Zn3=25kg/ha, Zn4=35kg/ha, Zn5=55kg/ha and Zn6=65kg/ha  ) was studied. The results showed that the effect of irrigation on seed storage proteins and protein yield was significant (P<0.01). Also results showed that effect of Zn fertilizer on seed storage proteins and protein yield was not significant. In non irrigation treatment  seed storage proteins was increased compared to irrigation treatment and protein yield decreased. Also, results showed that no effects treatments (irrigation and Zn fertilizer) on protein banding patterns. Also, results indicated that not obvious any new band and not deleted any bands in all treatments
    Keywords: Irrigation, Protein, Seed
  • Hamze Esalat Nejad, Ahmad Esalat Nejad Pages 1315-1319

    The medicinal part of Rubia tinctorum is the dried root. The small yellowishgreen flowers are in loose, leafy, long-peduncled terminal or auxiliary cymes. The margin of the calyx is indistinct, 4- to 5-sectioned and has a tip that is curved inward. There are five stamens and an inferior ovary. The fruit is a black, pea-sized glabrous, smooth drupe containing two seeds. The perennial plant grows to a height of 60 to 100 cm. The pencil thick rhizome creeps widely underground. The stem is quadrangular with backward turning prickles at the edges

    Keywords: Rubia tinctorum, Madder, Dyeing wool, Red color
  • Saman Hajmohamadi *, Saeedreza Hajmohamadi Pages 1320-1331
    The objectives of this experiment were to investigate the application of new ligands including different atoms & evaluation their nucleophile effects against various metals. Chemistry researchers are really interested in this field. From among various ligands, there are some ligands with different coordinating ligands as well. There are great number of intermediate complexes and major elements of organic compositions with various atoms. There is a regular adding of new compositions. Complexes are the most important chemical combinations with various catalysts and biological, medicine and other applications. Those complexes with ligands including different atoms givers are really important and their synthesis could solve most of chemical problems. Supplying of new ligands is an important and key part of coordination chemistry which may cause some varieties and different properties in complexes with equal central nucleus. As a result, this research has evaluated new ligands including different coordination atoms (such as Oxygen, Nitrogen and …) along with their behavior against various metals like Copper, Nickel, Iron and...
    Keywords: Ligands, Nucleophile, Iron, Cobalt, copper
  • Ali Olfati *, Gholamali Moghaddam, Mitra Bakhtiari Pages 1332-1336
    The bio-stimulation technique offers a potentially useful and practical way for reproductive performance in rams. Reports on how bio-stimulation affects sexual potency rams are scarce: Knowledge of how rams respond to bio-stimulation is useful for persons who involved in semen collection; "hand" (controlled) mating, and the administration of sexual performance evaluations. The reduction of the stimulus value of the ewes after several, or even after one mating, appears to be the major factor accounting for the temporary interruption of the sexual activity of the rams. Sexual stimulation provided a definite, clearly recognizable end point for establishing that a ram was sexually stimulated
    Keywords: Biostimulation, Rams, Reproductive performance
  • AliAsghar Bagheri *, Sara Saadatmand, Vahid Niknam, Taher Nejadsatari, Valiollah Babaeizad Pages 1337-1350

    Abiotic stresses including salinity are the major limiting factors of growth and crop production worldwide. Microbial endophytes as the most important soil microorganisms, by modifying plants at genetical, physiological and ecological levels increase their yield per area unit and provide the possibility of crop production in saline and arid soils or climates with biotic and abiotic stresses. The endophytic fungus, Piriformospora indica has a pronounced growth-promoting activity and also increases plant resistance to environmental stresses including salinity, drought and plant pathogens. We compared some growth parameters, physiological and biochemical responses such as total soluble proteins, Relative Water Content(RWC), lipid peroxidation, free proline content, and enzyme antioxidants(catalase, glutathione reductase, superoxide dismutase, ascorbate peroxidase) activity of p.indica–inoculated and non-p.indica-inoculated(controls) rice(Oryza sativa) under salt stress. The obtained results show that P. indica increase the biomass of aerial parts and root, total soluble proteins, Relative Water Content (RWC), free proline content and enzyme antioxidants activity of inoculated rice in compared to the controls. In contrast, Lipid peroxidation decreased in inoculated rice in compared to the controls. The obtained results of this research indicated that the effective role of this fungus to improve growth of rice under salt stress conditions

    Keywords: Antioxidant enzymes, Piriformospora indica, Rice (Oryza sativa), Salt stress
  • Behzad Babazadeh Darjazi * Pages 1351-1363

    Studies have shown that oxygenated compounds and TSS are important in food products. It seems that cultivars have a profound influence on these factors. The goal of the present study is to investigate on flavor components and juice quality parameters of two mandarin cultivars. In the last week of January 2012, at least 10 mature fruit were collected and their peel oil was extracted using cold-press and eluted using n-hexane, then analyzed using GC and GC-MS. TSS were determined using a refractometer. Data were analyzed using one-way analysis of variance (ANOVA) and Duncan’s multiple range tests. The amount of aldehydes ranged from 0.19% to 1.09%. TSS ranged from 7.6% to 9.8 %. Between two cultivars examined, Willow leaf showed the highest content of aldehydes and TSS. As a result of our study, we can conclude that the cultivars used can influence the quantity of oxygenated compounds present in the oil and TSS present in the juice

    Keywords: Flavor components, Juice quality, Peel oil, Mandarin cultivars
  • SayedAli Ahmadi *, Meysam Maddahi Pages 1364-1367

    Reaction of Glycin with Malononitrile afforded respective Pyrrole. Pyrrole is one of the heterocyclic compounds with very important biological activities. Heterocycles are extremely important because of their wide range of applications that goes from their use as pharmaceuticals and agrochemicals to dyestuffs and additives. In this view, it was proposed to synthesize pyrrole-3-carbonitrile derivative. An efficient one-step protocol has been developed to make new molecules of this family. An expeditious synthesis of derivatives pyrrole has been developed by reacting Malononitrile  and Glycine derivatives using a microwave. The structures of synthesized were assigned on the basis of IR and 1H NMR spectroscopy data

    Keywords: Glycine, Malononitrile, Pyrrole
  • Vahid Beyginiya *, Mahmud Khoramivafa, Farhood Yeganehpoor, Farideh Samadiyan Pages 1368-1376
    The experiment was carried out in a factorial arrangement with the base of randomized complete block design in three repetitions. The first factor consisted of 11 bed for eating worm and the second factor is the different seasons (spring and autumn) respectively. Traits was including number of capsules (Coconut), the number of adult worms, the number of immature worms, live worms masses (mg), maximum weight per worm (mg) and the average number of outgoing cases per capsule (Coconut), respectively. The results showed that the interaction between the incubator × seasons was significant for all traits. So the highest average in 80% sheep manure + wheat straw 20% was observed in the spring.It wasconclude that changes in different contexts breeding seasons and has a great effect on the measured traits Maximum biomass, maximum activity was obtained in the spring mating and the number of capsules and the season tiny capsules Unexpectedly a winter was produced by the adult worm
    Keywords: environment, E. fetida worm, Worm biomass
  • Farideh Samadiyan, Ali Soleymani, Farhood Yeganehpoor, Vahid Beyginiya Pages 1377-1386

    The experimental was split plot in a randomized complete block design with three replications. In this experiment, different levels of nitrogen in the main plots included four levels (0, 50, 100 and 150 N) kg.ha-1 urea and wheat varieties, including cultivars, Sepahan and SW were placed in the subplots. Results showed that nitrogen fertilizer and cultivar were significant effects on maximum light absorption. Fertilizer treatment of 150 kg.ha-1 nitrogen resulted in maximum light absorption compare to other treatments. Maximum light absorption was related to Pishtaz cultivar. The interaction between nitrogen and cultivar on maximum light absorption was significant at 5% probability level. Treatment of 150 kg.ha-1 nitrogen with Pishtaz cultivar had the highest average of light absorption. As well as the calculated extinction coefficient of light during the growing season to control treatment, 50, 100 and 150 kg.ha-1 nitrogen was respectively equal to -0.4675,  -0.4794, -0.4858 and -0.495 and for Pishtaz, Sepahan and SW cultivars was -0.488, -0.4618 and -0.4504 respectively. Results indicate that in order to achievement to maximum light absorption, 150 kg.ha-1 nitrogen fertilizers together with Pishtaz cultivar at the condition similar to this study seems to be appropriate

    Keywords: Wheat, Fertilizer, Pishtaz cultivar
  • Nematollah Dayyani *, Morteza Beyki Bandar Abadi, Ahmad Amir Abadi Farhani Pages 1387-1391
    Chelating is the chemical process by which a mineral (iron, cobalt, copper, zinc, and manganese) is combined with a mixture of amino acids and peptides. The resulting substances are known as chelates. Another descriptive term, proteinates, refers to the amino acid bond. These chelated minerals are thought to be more digestible than nonchelated forms. In other words, chelation makes the minerals more bioavailable (able to be absorbed and used for bodily functions), chiefly by shielding them from the effects of other dietary elements in the animal’s digestive tract. Proteinates or chelates are described as organic minerals in contrast to inorganic minerals, those that are not bound to amino acids
    Keywords: Chelate, mineral, Nutrition, Bioavailability
  • Nematollah Dayyani *, Keyvan Karkudi, Hasan Bakhtiari Pages 1392-1396
    The reproductive performance of a dairy herd has a significant effect on the profitability of that herd. Common measures of reproductive performance are days to first service, days to conception, calving interval, services per conception, conception rate, estrus detection rate, and pregnancy rate. Most cow operations would benefit economically by reducing the number of operational days, decreasing culling rates due to non-pregnant females, and shortening their calving interval. Several factors influence reproductive performance, but none require more visual attention than heat or estrus detection
    Keywords: Reproductive, Performance, Dairy cattle
  • Nematollah Dayyani *, Keyvan Karkudi, Abbas Zakerian Pages 1397-1402
    Bacteria make up about half of the living organisms inside of the rumen. However, they do more than half of the work in the rumen. The bacteria work together. Some breakdown certain carbohydrates and proteins which are then used by others. Some require certain growth factors, such as B-vitamins, which are made by others. Some bacteria help to clean up the rumen of others’ end products, such as hydrogen ions, which could otherwise accumulate and become toxic to other organisms. This is called “cross-feeding”. Rumen microbiological studies based on laboratory culture have contributed greatly to our understanding of how feeds are transformed into the VFA and microbial cells that provide nutrients to the cow. Over the last 20 years, the limitations of culture-based microbiological studies of almost all microbial habitats become apparent
    Keywords: Microbiology, Rumen, Bacteria, pH, fungi
  • Phytate and Phytase in Poultry Nutrition
    Nematollah Dayyani *, Morteza Beyki Bandar Abadi, Ahmad Amir Abadi Farhani Pages 1403-1408

    This article was retracted due to plagiarism.

  • Nematollah Dayyani *, Hasan Bakhtiari Pages 1409-1413
    Heat stress and exhaustion is one of the top causes of chicken death. For those new to backyard chicken farming, it is important you learn to recognize the signs of this serious condition and how to keep your chickens cool and hydrated. Chicks, especially, need extra attention to help them remain healthy. For a flock of laying hens, knowing how to prevent heat exhaustion and treat a chicken suffering heat exhaustion is important to preserving their health and the health of their eggs. Once your chicks are old enough to move outdoors, remain vigilant for signs of heat stroke, especially if it’s mid to late summer. Heat stress comes on quickly so it is important to watch them closely. Even older birds need supervision during the hot summer months
    Keywords: Heat stress, Poultry, Chicken, Eggs
  • Homayoun Banani Rad *, Jamal Fayazi, Cyrus Amirinia, Hedayatolah Roshanfekr, Hamidreza Seydabadi Pages 1414-1422
    Pedigree information and phenotypic records are the key features in animal genetics and breeding. Otherwise best methods for genetic evaluation and estimation of parameters will be tending to no correct results. This study was aimed to investigate and verify pedigree relations among 76 individuals who were genotyped for 3 fluorescent labeled microsatellite markers picked up from FAO-ISAG joint recommended list as one multiplex PCR set. 11 sires, 11offspring and 11 dams with 43 unknown samples were analyzed. Based on exact allele sizes, 33 alleles were observed within the studied population. The mean number of alleles per locus was 11. Polymorphism information content (PIC) values ranged from 0.3257 to 0.8043 with the mean value of 0.6213. The most informative loci were :BM2113 (16alleles,PIC=0.7338), BM1818(3alleles,PIC=0.3257).The indices of genetic variability within population and polymorphism of loci including average heterozygosis, the number of observed and effective alleles, polymorphic information content (PIC) and so on showed that the studied  khouzestan buffaloes population and used markers have still a reliable diversity and polymorphism level, respectively. Also, combined probability of exclusion (PE) values obtained per all loci in both parentage and identification analysis was 0.9381 and 0/4483thatindicate the high efficiency of studied marker set for parentage and identification test in this population
    Keywords: Parentage testing, identification, khouzestan buffaloes population, Microsatellite markers
  • Shahriar Nessabian, Narjes Asadi * Pages 1423-1430
    The present article studies role of Iran  export insurance fund on agricultural export sector by during 1385-1391.Since activity in agricultural sector is one of the most dangerous economical activities, and the most important problem of planners and politicians of agricultural development reducing risk of economic activities and increasing security coefficient for producers of agricultural sector is very important. Export credit and insurance institutions are established generally by governments for supporting counties export. In fact, many studies are based on insurance and economic growth variables; however, there is little attention to role of credit insurance institutions especially in agricultural sector by researches
    Keywords: Agricultural export, Insurance institutions, Agricultural sector
  • Maryam Tarighati *, Vajihe Karbasizade, Sharareh Moghim Pages 1431-1435
    Herpetic keratitis which is resulted from herpes simplex virus type I, is considered the most common cause of corneal blindness that needs being diagnosed and treated in order to prevent irreversible eye effects. The best method to diagnose it is molecular method which has high sensitivity and exclusivity. The current study was done on 25 eye samples collected from patients referred to the Feyz hospital of Isfahan who were diagnosed with herpetic keratitis disease. After cornea sampling and extracting DNA from eye samples, LAMP-PCR technique was done to search genome of herpes simplex virus type I. Among 25 suspected cases of herpetic keratitis, 5 samples were confirmed to have genome virus of HSV1 and herpetic keratitis frequency was determined by 20%. The results of this investigation showed a relative high frequency of herpetic keratitis in this zone using LAMP-PCR diagnostic method compared with similar studies which indicates high sensitivity of this technique. Therefore, using such rapid, accurate and cheap molecular method is suggested
    Keywords: Herpes simplex virus type I, Herpetic keratitis, LAMP-PCR
  • Soheil A. Alizadeh, Alireza Pazoki *, Hasan Habibi Pages 1436-1451
    To evaluate the effect of ascorbate and gibberellin on some morphological traits and relative water content of medicinal plant fenugreek in different levels of salinity, an experiment was carried out in Shahr- e - Rey branch of Islamic Azad University in October 2012. The experiment was arranged as factorial experiment in the basis of completely randomized design with four replications. The experimental factors included four salinity levels (0, 30, 60 and 90 mM), three ascorbate levels (0, 3 and 6 mM) and two gibberellin levels (0 and 2 mM). The results showed that, the simple effect of salinity, gibberellin and ascorbate on experimented traits were significant. Except double effects of gibberellin and ascorbate on stem length, leaf area interaction effects of salinity and ascorbate on relative water content, all double and triple interaction effects on experimented traits were not significant. The findings of the salinity simple effects indicated that, increase in salt concentration reduced the amount of concerned traits. So that the lowest biomass, vegetative growth and RWC were obtained in salinity by 90 mM. Gibberellin and ascorbate application could decrease adverse effects of stress, so that, by spraying these compounds on the plant, an increase was observed in leaf vegetative growth and relative water content.
    Keywords: Fenugreek, ascorbate, Gibberellin, Salinity stress, morphological traits
  • Ali Olfati *, Gholamali Moghaddam, Mitra Bakhtiari Pages 1452-1456
    Thin ewes or very over-conditioned ewes and ewes carrying multiple pregnanciesare more likely to develop pregnancy toxemia (ketosis). Pregnancy toxemia is a metabolic disorder characterized by hypoglycemia and hyperketonemia resulting from incapacity of the ewes to maintain adequate energy balance (usually in the last 5-6 weeks).Available information about pregnancy toxemia focuses mainly on pathogenic mechanisms and clinical features, early diagnosis, and therapeutic options. However, the pathophysiology and metabolic changes of this disorder remain poorly understood. An immediate and accurate diagnosis usually increases the possibility for their successive treatment and prevention. The objective of this review was to increase awareness of the disease, its likely cause, and practical treatment and prevention measures
    Keywords: Diagnosis, Pregnancy toxemia, prevention, Sheep, Treatment
  • Ali Salehi Sardoei *, Hasan Sarhadi, Parviz Rahbarian, Monir Rohany Yazdi, Mina Arbabi, Masoumeh Jahantigh Pages 1457-1465
    The effect of Gibberellic Acid (GA3) and Benzyladenine (BA) on Aloe vera was evaluated at pot cultivation conditions. This study was performed in two factorial test based on complete random plan and 4 repeats with 12 treatments. The main factor was included spraying, drip and spraying + drip. Secondary factor was included concentrations of GA3 and BA at 0, 100, 200 and 400 mg.L-1 levels. The number of Offset was increased by addition of GA3 and BA levels. The results show that the number of Offset has been better in drip application than spraying method. The use of drip+spraying method has caused improve in the plant than other methods. The maximum offset was obtained in 400 mg.L-1 concentration of BA
    Keywords: Aloe vera, Application Methods, Offset, Pot cultivation
  • Ali Salehi Sardoei *, Hasan Sarhadi, Parviz Rahbarian, Monir Rohany Yazdi, Mina Arbabi, Masoumeh Jahantigh Pages 1466-1470
    Studies have shown that rooting substrate is one of the effective factors at rooting of hard rhizogenetic plant such as Henna. The purpose of this study is to determine an appropriate concentration of Naphthalene Acetic Acid (NAA), Indole Butyric Acid (IBA) and salicylic acid (SA) on Rooting of Henna. Present study showed that there was a great variation in most of the measured characters at P< 0.05 percent level. The obtained results show that hormonal treatments have caused the increase of percent of rooting. The use of SA caused a positive effect on rooting. The maximum leaf was obtained in 2000 ml.L-1 NAA + 200 ml.L-1 SA. This study shows that Plant Growth Regulators have a profound influence on Rooting of Henna
    Keywords: Cuttings, Henna, IBA, NAA, Rooting, Salicylic acid
  • Nasrin Jalilian *, Reza Mahmoudzadeh, Mansour Rezaei, Mitra Bakhtiari Pages 1471-1477

    The present study evaluate the histopathologic findings and clinical indications in hysterectomized patients based on sonographic assessments. This study population consisted of all patients who were referred to the Pathology Ward of Imam Reza educational and treatment Center (Kermanshah, Iran) during March 2006 to May 2012. The samples were stained with hematoxylin-eosin after fixation in formalin. 636 cases of hysterectomy were examined. 232 patients (50.7%) underwent salpingo oophorectomy. The most cases of hysterectomy have been performed in multipara women. The most common indications for trans-abdominal hysterectomy were fibroma (in 38.8% of cases), adenomyosis, ovarian cancer, uterine cancer and endometrial hyperplasia, respectively. The histopathologic results showed that fortunately benign diseases were the most common findings in hysterectomy cases

    Keywords: Hysterectomy, Histopathology, Abnormal uterine bleeding, Endometrial hyperplasia, Uterine cancer
  • Ashkan Nabavi Pelesaraei *, Sajjad Shaker Koohi, MohammadBagher Dehpour Pages 1478-1489

    This paper studies the modeling and optimization of energy use and greenhouse gas emissions of eggplant production using artificial neural network and multi-objective genetic algorithm in Guilan province of Iran. Results showed that the highest share of energy consumption belongs to diesel fuel (49.24%); followed by nitrogen (33.30%). The results indicated that a total energy input of 13910.67 MJ ha-1 was consumed for eggplant production. In ANN, the Levenberg-Marquardt Algorithm was examined to finding best topology for modeling and optimization of energy inputs an GHG emissions for eggplant production. The results of ANN indicated the best topology with 12-9-9-2 structure had the highest R2, lowest RMSE and MAPE.  Also, the multi-objective optimization was done by MOGA. In this research, 42 optimal was introduced by MOGA based minimum total GHG emissions and maximum yield of eggplant production, in the studied area. Also, the results revealed that the best generation with lowest energy use was consumed about 4597 MJ per hectare. The GHG emissions of best generation was calculated as about 127 kg CO2eq. ha-1. The potential of GHG reduction by MOGA was computed as 388.48 kg CO2eq. ha-1. Also, the highest reduction of GHG emissions belongs to diesel fuel with 65.05%

    Keywords: Eggplant, energy consumption, Greenhouse gas emissions, Modeling, Optimization
  • Arman Jalali *, Hossein Ghaffari, Farshad Soheilifard Pages 1490-1504
    One of the main factors that cause to quality loss for fresh fruit market apples is bruise damage. Amongst the factors that affect apple sensitivity to bruising, major one is drop height and area profile during the impact. In the present study, four Iranian apple varieties consisted of Atirli, Kapak, Kowse and Paiez that were selected and 100 fruits of each variety were picked up, then apples were dropped from three heights and some mechanical properties such as bruise diameter, bruise height, rebound height, bruise energy percent, bruise coefficient of restitution, bruise resistant percent, bruise volume, bruise energy absorb and bruise contact above were tested and measured. The value of all features found to be different from variety to variety. As a result, Paiez variety was firmer than others. The maximum coefficient of static friction for MDF and the minimum was for PVC
    Keywords: Bruise, Fruit, Local, Static friction coefficient
  • SeyedMahdi SeyedHosseini *, MohammadAgha Mohammadi, Mohsen Mousavi Pages 1505-1511

    In the present study, theoretical chemical reactivates Photo isomerization in Cis-Retinal as a Natural Photo switch in Vision. DFT hybrid functional, B3LYP and, post-HF method, were the theoretical methods applied utilizing G09 software. 6-31G+ (d,p) basis set employed for structural optimizations, and single point computations performed using B3LYP/6-31G+(d,p). The isomers cis molecule retinal from 0 to 180 ° in steps of 10 degrees to the trans isomers convert and we calculate the energy in each step, we determined that the most appropriate angle for the conversion of isomers of cis to trans angleq =  90.11 ° the energy barrier less be.It identified that transmission S0® S1 is the most likely transmission

    Keywords: Photoisomerization, Retinal, Photo switch, DFT, B3LYP
  • Hamid Reza Guodarzi *, MohammadAgha Mohammadi, Mohsen Mousavi Pages 1512-1517

    Amyloid-β (Aβ) self-assembly into cross-β amyloidfibrils is implicated in a causative role in Alzheimer’s disease pathology.Uncertainties persist regarding the mechanisms of amyloid self assembly and the role of metastable prefibrillar aggregates. Aβ fibrilsfeature a sheet-turn-sheet motif in the constituent β-strands; as such, turn nucleation has been proposed as a rate-limiting step in the self assembly pathway. Herein, we report the use of an azobenzene β-hairpin mimetic to study byUsing Density Functional Theory the role turn nucleation plays on Aβ self assembly.[3-(3-Aminomethyl) phenylazo] phenyl acetic acid (AMPP)was incorporated into the putative turn region of Aβ42 to elicit temporal control over Aβ42 turn nucleation; it was hypothesized that self-assembly would be favored in the cis-AMPP conformation if β-hairpin formation occurs during Aβ self-assembly and that the trans-AMPP conformer would display attenuated fibrillization propensity. It was unexpectedly observed that the trans-AMPP Aβ42Additionally, cis-trans photo isomerization resulted in rapid formation of native-like amyloid fibrils and trans−cis conversion in the fibril state reduced the population of native-like fibrils. Thus, temporal photo control over Aβ turn conformation providessignificant insight into Aβ self-assembly

    Keywords: Amyloid-β, Turn nucleation, Alzheimer’s Disease, β-turn, amyloid fibrils, Azobenzene photoswitch, DFT, B3LYP