text:
Delayed Diagnoses of SGCE MyoclonusDystonia
Authors: {'first_name': 'M. Georgeta', 'last_name': 'Varga'},{'first_name': 'Nikita P.', 'last_name': 'Nand'},{'first_name': 'Mark S.', 'last_name': 'LeDoux'}
Background: Myoclonus-dystonia due to SGCE mutations (OMIM: 159900) most commonly presents during childhood with mainly upper body myoclonus, and mild dystonia affecting the neck and arms.
Case reports: Herein, we report patients misdiagnosed during childhood with Tourette syndrome and dyskinetic cerebral palsy, and, during adulthood, found to harbor SGCE frameshift mutations.
Discussion: Myoclonus-dystonia may be underdiagnosed due to phenotypic misclassification during childhood. SGCE mutations should be included in the differential diagnosis of childhood movement disorders that ostensibly manifest with tics, myoclonus, or abnormal posturing secondary to dystonia and/or spasticity.
Highlights: Due to pleiotropy, variable penetrance, broad differential, and hereditary effects of imprinting, the diagnosis of a disorder of childhood onset, myoclonus-dystonia due to SGCE mutations, may be delayed until adulthood, often compromising appropriate clinical management and genetic counseling.
Keywords: SGCE, myoclonus, dystonia, tics, cerebral palsy, Tourette syndrome
DOI: http://doi.org/10.5334/tohm.334
Accepted on 17 May 2020 Submitted on 13 May 2020
Mutations in SGCE (Chr 7q21.3), a maternally imprinted gene, have been causally linked to Myoclonus-Dystonia syndrome (M-D, DYT-SGCE, OMIM: 159900) [1]. Classically and most commonly, this disorder is characterized by childhood onset of myoclonus and dystonia [2]. Patients typically present with upper-body predominant, alcohol-responsive myoclonic jerks, along with cervical and arm dystonia [2]. Psychiatric co-morbidities including depression, anxiety, bipolar disorder, phobias, alcoholism, and obsessive-compulsive disorder have also been associated with M-D and tend to worsen over the disease course [3, 4]. These psychiatric manifestations may occur in isolation in some members of affected pedigrees. In addition, the neuropsychiatric spectrum of SGCE mutations is broad and may include early gait dysfunction with leg involvement [5] and, more rarely, cognitive dysfunction [6]. Penetrance is incomplete and notable intrafamilial and extrafamilial phenotypic variability is well established [7]. Early and correct diagnosis may facilitate appropriate pharmacological and surgical interventions, and genetic counseling. We present two cases of genetically confirmed SGCE myoclonus dystonia, initially misdiagnosed as Tourette syndrome (Case 1) and dyskinetic cerebral palsy (Case 2), respectively.
Case 1. A 32-year-old right-handed female presented to our movement disorders clinic with abnormal movements with onset at 7 years of age. Historically, these movements were described as involuntary, brief, jerky movements of the hands, shoulders, neck and trunk. These movements were previously classified as tics by prior treating neurologists, and she had been diagnosed with Tourette syndrome. During her adult years, she recognized that her involuntary movements were exacerbated by caffeine intake and improved with alcohol. She reported a history of abnormal vocalization described as "throat clearing" but compatible with laryngeal myoclonus. There was no history of head trauma or neuroleptic use. Neuropsychiatric review of systems was pertinent for mild anxiety of 20 years' duration. Family history was significant for reported "tic-like" movements in her father and obsessive-compulsive disorder (OCD) in her mother (Figure 1, Pedigree 1). Previously, she had been treated with tetrabenazine 12.5 mg PO TID and clonazepam 0.5 mg PO BID. Tetrabenazine was not tolerated due to worsened anxiety. Clonazepam showed no significant clinical benefit. On neurological examination, action myoclonus of the arms and trunk was apparent. There was no dystonia, motor tics, phonic tics, or phonic myoclonus. There has been a greater than 50% improvement in myoclonus with deutetrabenazine (6 mg PO BID) The positive response to deutetrabenazine has been sustained for over one year and the patient has not been interested in taking higher dosages of deutetrabenazine. Testing for an SGCE mutation was pursued given the characteristic historical and visual presence of upper body action myoclonus of childhood onset, positive family history of a movement disorder and OCD, and alcohol responsiveness. Bidirectional Sanger sequencing identified a heterozygous single base pair deletion (GRCh38/hg38, NC_000007.14: g.94603404delT, NM_001099401.1(SGCE_v001): c.711delA, p.Glu238Lysfs*9). This frameshift mutation is predicted to alter the length of the ε-sarcoglycan reference protein of 462 residues to a protein of 245 residues. The location of the mutation most likely leads to nonsense mediated decay of SGCE transcripts.
Pedigree 1: I, II, III Generation, Full symbols symptomatic individuals, Slashed symbols deceased individuals, II-2 Father with tic-like movements, III-3 Mother with OCD, III-1 Patient with + DyT11.
Pedigree 2: I, II, III Generation, Full symbols symptomatic individuals, Slashed symbols deceased individuals, I-1 Paternal Granfather with tic-like movements, deceased, III-1 Sister with jerky movements, III-2 Patient with + DyT11.
Case 2. A 64-year-old left-handed male presented to our movement disorders clinic with a history of involuntary movements since childhood and mild developmental delay. He was delivered by Cesarean section (C-section) at 7 months of gestation due to fetal distress and was diagnosed with pulmonary hypoplasia. However, he experienced an unremarkable early postnatal course. He had mildly delayed gross and fine motor milestones without intellectual disability. At 8 years of age, he began to manifest involuntary "jerky" movements mainly involving his upper extremities. During childhood and early adulthood, he was assessed by two independent neurologists. Diagnostic work-up included a normal brain magnetic resonance imaging (MRI) brain scan and normal electroencephalogram. One neurologist provided a provisional diagnosis of dyskinetic cerebral palsy. Reportedly, the "jerky" movements were mild but persistent over the subsequent four decades and did not interfere with physical activity. However, at age 45, he experienced worsening of clinical signs with more pronounced "jerking" of his arms, neck and shoulders. Changes in speech with a weak and breathy voice that improved with whispering were also reported. Amelioration of symptoms could only be achieved by drinking alcohol. He had long-standing mild generalized anxiety. Previous treatment with phenobarbital, levetiracetam, and clonazepam had been ineffective. Family history was significant for mild "jerky" movements in his sister and paternal grandfather (Figure 1, Pedigree 2). Clinical examination was notable for spontaneous myoclonic movements involving the axial and shoulder girdle muscles and arms that worsened with activity. Additionally, mild cervical dystonia and mixed vocal dystonia (clinically pharyngeal and laryngeal involvement) was noted. However, this patient was not assessed with laryngoscopy and videostroboscopy. The remainder of the general physical and neurological examinations was unremarkable. Deutetrabenazine caused fatigue and was of no significant clinical benefit at a dosage of 9 mg PO BID. Given his characteristic myoclonic and dystonic features on clinical examination, positive family history, and response to alcohol, SGCE was assessed with bidirectional Sanger sequencing which permitted identification of a heterozygous single base pair deletion (GRCh38/hg38, NC_000007.14: g.94618801delT, NM_001099401.1(SGCE_v001): c.619delA, p.Arg207Glyfs*12). Rather than translation of a truncated protein of 217 residues, the location of the stop codon most likely precipitates nonsense mediated decay of SGCE transcripts. This patient has been offered deep brain stimulation (bilateral globus pallidus internus) for treatment of his myoclonus-dystonia.
Unfortunately, our two cases illustrate the poignant realty that the diagnosis of childhood onset myoclonus-dystonia can be delayed for decades. The delayed diagnoses in our two pedigrees also suggests that myoclonus-dystonia and SGCE-associated neuropsychiatric disorders may be significantly underdiagnosed. For patients with a characteristic clinical picture, SGCE mutations are the most common known etiology for this neuropsychiatric disorder [8] and genetic testing should be pursued in these cases unless limited by financial considerations. SGCE-linked myoclonus-dystonia may show clinical similarities to tics, spasticity, dystonic tremor, epilepsy, and conversion disorders with positive motor features. While characterized by mainly upper body (arms and trunk) myoclonus and mild focal or segmental dystonia (neck, distal arms), a broad array of atypical neuropsychiatric presentations and manifestations are well documented in the existing literature [9].
Use of a published diagnostic algorithm for myoclonus [10], and then diagnostic criteria for M-D [8], are the first steps in differentiating M-D from other neurological disorders. Generally, in patients with M-D, myoclonus predominates over dystonia and onset is prior to adulthood. Our two patients had been incorrectly diagnosed with Tourette syndrome and dyskinetic cerebral palsy. In contrast to myoclonus, tics are typically more complex, suppressible for brief periods, and often precipitated by a premonitory urge. Brain MRI is frequently abnormal in dyskinetic cerebral palsy and the dystonic and choreoathetoid movements characteristic of this disorder are usually much slower than myoclonus. The developmental time course of disease manifestations can also help to distinguish M-D from other pediatric movement disorders. In this regard, some M-D patients exhibit mild lower extremity dystonia and associated gait dysfunction during childhood or adolescence that subsequently resolves [11].
There are other potential reasons for a delay in diagnosis. Maternal imprinting and intrafamilial phenotypic variability can complicate interpretation of family history and lead to dismissal of hereditary etiologies in differential diagnoses. Although useful historical information, the response to consumption of alcoholic beverages is uncommonly available in children and adolescents. In some cases, no connection is made between the psychiatric and motor phenotypes, which may be considered as separate diseases. Neurological manifestations, particularly dystonia, may be subtle and mild psychiatric manifestations such as anxiety and depression may have not undergone treatment for decades. Finally, dystonia can be present in childhood and then abate.
Delayed diagnosis of M-D can have a significant impact on patients and their families. In particular, a prompt etiological diagnosis can inform treatment decisions and caregiver concerns [12]. M-D may benefit from occupational and physical therapy, and often responds to specific pharmacological interventions (tetrabenazine, anticholinergics, and zonisamide) and electrical stimulation of the globus pallidus [8, 13, 14, 15], and, as reported here, deutetrabenazine may be an additional therapeutic option. Earlier surgical intervention in patients with severe disease and inadequately responsive to oral pharmacotherapy and/or injections of botulinum toxin may improve long-term outcomes [16]. Earlier diagnosis may reduce alcoholism [4] and prompt recognition of psychiatric co-morbidities allowing these to be symptomatically managed before they exert deleterious effects on academic performance, work productivity and social interactions. Prompt etiological diagnosis of M-D may also facilitate academic, career and family planning [12].
Genetic testing should begin with Sanger or next-generation sequencing and, ideally, confirmation with bidirectional Sanger sequencing. Sequencing should cover all coding exons, exon-intron boundaries, and the core promoter region of SGCE. Genetic testing should also include exclusion of exonic, multi-exonic and interstitial deletions, particularly in patients with typical clinical presentations and absence of single nucleotide changes or small indels [17]. Genetic testing for SGCE mutations should be considered in "scan normal" cases of putative cerebral palsy [18]. Genetic counseling should include consideration of maternal imprinting, pleiotropy, and variable penetrance.
Ethics and Consent
Our case reports do not meet the definition of human experimentation. No personally identifiable information has been included in case descriptions.
Dr. LeDoux was funded by the Dystonia Medical Research Foundation and Benign Essential Blepharospasm Research Foundation.
Dr. Varga is a consultant for USWorldMeds, Medtronic, and Abbott; speaker for Adamas Pharmaceuticals, Acadia Pharmaceuticals, Teva Pharmaceutical Industries, USWorldMeds, Acorda Therapeutics and Lundbeck; and received research funding from The Military Order of the Purple Heart and research equipment from Boston Scientific. Dr. LeDoux is a consultant for USWorldMeds; speaker for Adamas Pharmaceuticals, Acadia Pharmaceuticals, Teva Pharmaceutical Industries, USWorldMeds, Kyowa Kirin, and Acorda Therapeutics; and receives publishing royalties from Elsevier (Animal Models of Movement Disorders, and Movement Disorders: Genetics and Models) and TheBookPatch (Parkinson's Disease Poetry). Dr. LeDoux's research has been funded by the Michael J. Fox Foundation, National Institutes of Health, Axovant Sciences, Wave Life Sciences, Teva Pharmaceutical Industries, Pharma Two B, Dystonia Medical Research Foundation, and Benign Essential Tremor Research Foundation.
The authors have no competing interests to declare.
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text:
Curriculum ScienTI
Electron. J. Biotechnol. vol.17 no.3 Valparaíso mayo 2014
Synthesis of silver nanoparticles using a biosurfactant produced in low-cost medium as stabilizing agent
Charles B.B. Fariasa, b, Aline Ferreira Silvaa, Raquel Diniz Rufinoa, b, Juliana Moura Lunaa, b, José Edson Gomes Souzaa, Leonie Asfora Sarubboa, b*
a Centro de Ciências e Tecnologia, Universidade Católica de Pernambuco, Rua do Príncipe, Boa Vista, Recife, Pernambuco, Brazil.
b Centro de Gestão de Tecnologia e Inovação, Rua da Praia, São José, Recife, Pernambuco, Brazil.
A biosurfactant produced by Pseudomonas aeruginosa cultivated in a low-cost medium formulated with 2.5% vegetable oil refinery residue and 2.5% corn steep liquor and distilled water was employed to stabilize silver nanoparticles in the liquid phase. The particles were initially synthesized using NaBH4 as reducing agent in biosurfactant reverse micelles and were extracted from the micellar solution to disperse in heptane.
A silver particle size in the range of 1.13 nm was observed. The UV–vis absorption spectra proposed that silver nanoparticles could be formed in the reverse micelles and relatively stabilized for at least 3 months without passivator addition. The Transmission Electron Microscope (TEM) shows that the silver nanoparticles are of spherical form and relatively uniform.
This process provided a simpler route for nanoparticle synthesis compared to existing systems using whole organisms or partially purified biological extracts, showing that the low-cost biosurfactant can be used for nanoparticle synthesis as a non-toxic and biodegradable stabilizing agent.
Keywords: Microbial surfactant; Nanoscale materials; Pseudomonas aeruginosa.
The application of nanoscale materials and structures, usually ranging from 1 to 100 nanometers (nm), is an emerging area of nanoscience and nanotechnology. Nanomaterials may provide solutions to technological and environmental challenges in the areas of solar energy conversion, catalysis, medicine, and water treatment [1] and [2]. This increasing demand must be accompanied by "green" synthesis methods. In the global efforts to reduce generated hazardous waste, "green" chemistry and chemical processes are progressively integrating with modern developments in science and industry. Implementation of these sustainable processes should adopt the 12 fundamental principles of green chemistry [3], [4], [5] and [6]. These principles are geared to guide in minimizing the use of unsafe products and maximizing the efficiency of chemical processes. Hence, any synthetic route or chemical process should address these principles by using environmentally benign solvents and nontoxic chemicals [7].
Silver nanocrystallites exhibit an enhancement of some potential properties including catalysis [8], magnetic and optical polarizability [9], electrical conductivity [10], and antimicrobial activity in surface-enhanced Raman scattering (SERS) [11]. Currently, many techniques have been devoted to synthesizing nanosized silver particles, such as chemical reduction [12], [13] and [14], photochemical reduction, reverse micelle based and lamellar liquid crystal approaches [15], aerosol techniques and an electrostatic spraying technique [16]. Since the reverse micelle system has been used to form metal nanoparticles, this method has been paid more and more attention [17]. However, most surfactants we used were chemical surfactants, which are toxic and will pollute the environment. Biosurfactants, which derived from microbial origin, have bulky and complicated structures, higher biodegradability, lower toxicity, and excellent antiviral activities [18]. So biosurfactant as a "green" stabilizer is one of the best candidates. It is believed that biosurfactants will be increasingly attractive as multifunctional materials for the new century [14].
In the present paper the possibility of synthesizing silver nanoparticles in water-in-oil microemulsion stabilized by a low-cost biosurfactant is studied. The silver nanoparticles obtained are characterized by UV–vis absorption spectrum and a Transmission Electron Microscope (TEM).
2.1. Materials
n-Heptane and n-butanol were purchased from Sigma-Aldrich Chemical Corporation, USA. Silver nitrate (AgNO3) was purchased from Sigma-Aldrich Chemical Corporation, USA. Sodium borohydride (NaBH4, 97%) was purchased from Sigma-Aldrich Chemical Corporation, USA. All of the components are of reagent grade and used without further purification. Milli-Q grade water was used in all the experiments.
2.2. Bacterial strain and preparation of seed culture
A strain of Pseudomonas aeruginosa UCP0992 was provided from the culture collection of the Centre of Research in Environmental Sciences, Universidade Católica de Pernambuco, Brazil, registered with the World Federation of Culture Collections (WFCC). The cultures were maintained in nutrient agar slants at 4°C. For pre-culture, the strain from a 24 h culture on nutrient agar was transferred into 50 ml nutrient broth to prepare the seed culture. The cultivation condition for the seed culture was 28°C, 150 rpm, and 10–14 h of incubation time.
2.3. Biosurfactant production
For liquid fermentation, a 1% cell suspension of 0.7 OD (optical density) at 600 nm, corresponding to an inoculum of 107 C.F.U./ml, was inoculated into a 500 ml flask containing 100 ml medium consisting of distilled water amended with 5% vegetable oil refinery residue and 2.5% corn steep liquor. The pH of the medium was initially adjusted to 7.0 by 1.0 M HCl. The culture temperature and agitation rate were 37°C and 150 rpm, respectively. At the end of fermentation (120 h), samples were taken from the liquid culture to determine the surface tension and surfactant concentration.
2.4. Biosurfactant isolation
The biosurfactant was extracted from culture media after cell removal by centrifugation at 5,000 × g for 30 min. The supernatant pH was adjusted to 2.0 with 6.0 M HCl, and an equal volume of CHCl3/CH3OH (2:1) was added. The mixture was vigorously shaken for 15 min and allowed to set until phase separation. The organic phase was removed and the operation was repeated twice again. The biosurfactant was concentrated from the pooled organic phases using a rotary evaporator. The viscous yellowish product obtained was dissolved in methanol and concentrated again by evaporation of the solvent at 45°C [19].
2.5. Surface tension
Surface tension and interfacial tension (against hexadecane) changes were carried out on the cell-free broth obtained by centrifuging the cultures at 5,000 × g for 20 min by the ring method using a Sigma 70 Tensiometer (KSV Instruments Ltd. — Finland) at room temperature. Tensiometers determine the surface tension with the help of an optimally wettable ring suspended from a precision balance. In the ring method the liquid is raised until contact with the surface is registered. The sample is then lowered again so that the liquid film produced beneath the liquid is stretched. As the film is stretched a maximum force is experienced, the force is measured and used to calculate the surface tension. The instrument was calibrated against Milli-Q-4 ultrapure distilled water (Millipore, Illinois, USA). Prior to use the platinum plate and all the glassware were sequentially washed with chromic acid, deionized water, acetone and finally flamed with a Bunsen burner.
2.6. Preparation method
The nanoparticles were synthesized using two modified approaches, according to Xie et al. [20] and Palanisamy and Raichur [21].
For the synthesis of silver nanoparticles in situ in the water-in-oil microemulsion phase, a 0.05 mol/l aqueous AgNO3 solution and a 0.1 mol/l aqueous NaBH4 solution were separately used instead of water to form reverse micelles with the biosurfactant. NaBH4 was used here to act as reducing agent.
The first synthesis involved mixing 1.0 ml of 0.05 mol/l aqueous AgNO3 solution, 0.1 g/l biosurfactant and 25 ml n-heptane together and stirred vigorously at room temperature until homogeneous reverse micelles formed and the same bulk of 0.1 mol/l aqueous NaBH4 solution was used to replace aqueous AgNO3 to form the other reverse micelles. The two samples were mixed under stirring for 60 min. Then, the particles were precipitated from the solution and isolated by centrifugation at 14,000 × g. Then, 0.5 ml ethanol was added for each 1 ml reverse micelles. Ethanol was added to the complete removal of the surfactant and n-heptane. The prepared silver nanoparticles could be readily redispersed to obtain a suspension in 10 ml n-butanol aided by sonication.
The second microemulsion was prepared by dissolving 0.1 g/l of the biosurfactant in 6.25 ml of n-heptane and 1 ml AgNO3. Solution was added to the mixture with continuous stirring for 10 min at room temperature. Then, 1 ml NaBH4 was added to the mixture which was agitated for 30 min. After agitation, 10 ml ethanol was added to break the reverse micelles, thus forming two phases. The precipitate was separated by centrifugation at a speed of 14,000 × g for 30 min and 10 ml of n-butanol was added to obtain a suspension.
2.7. Characterization
The resulting samples were used for absorption spectroscopy characterization on a Shimadzu UV-2450 spectrophotometer from 300 to 800 nm. A FEI Tecnai™ (USA) TEM operated at 200 kV was used for studying the shape and size of the nanoparticles. The sample for TEM study was prepared by dispersing the powder particles in acetone solution followed by sonication for 5 min. A droplet of the solution mixture was taken on a carbon coated copper grid.
The green synthesis of silver nanoparticles involves three main steps, which must be evaluated based on green chemistry perspectives, including (1) selection of solvent medium, (2) selection of environmentally benign reducing agent, and (3) selection of nontoxic substances for the silver nanoparticle stability [22].
Considering the need of greener bioprocess and novel enhancers for the synthesis using microbial processes, biosurfactants and/or biosurfactant producing microbes are emerging as an alternate source of rapid synthesis of nanoparticles [19] and [23]. Micro-emulsion techniques using oil–water–surfactant mixture were shown to be a promising approach for nanoparticle synthesis, as described by Xie et al. [20].
Based on this approach, we have produced and tested a low-cost biosurfactant as a stabilizing agent of silver nanoparticles synthesized in microemulsion.
The biosurfactant from P. aeruginosa cultivated in a low-cost medium formulated only with two agro-industrial substrates was produced during 120 h at 37°C. The medium surface tension was reduced to 29.0 mN/m at the end of fermentation and the isolated biosurfactant corresponded to a concentration of 7.4 g/l.
3.1. Absorption spectra characterization
The result showed that a silver particle size in the range of 1.13 nm was obtained by the use of the biosurfactant from P. aeruginosa.
The UV–vis absorption band of nanoparticles at 400 nm is a typical characteristic of silver nanoparticles (Fig. 1). Metal nanoparticles have a surface plasmon resonance absorption in the UV–vis region. This result evidenced that the nano-scale silver can be synthesized in reverse micelles using glycolipid as stabilizer [24], [25], [26] and [27]. The particles are extracted from micelles by adding ethanol to the microemulsion. This result indicates that the nano-scale silver can be synthesized in reverse micelles using the low-cost biosurfactant as stabilizer. Decrease in the intensity is due to a change in the free electron density.
Fig. 1. UV–vis absorption spectra of silver nanoparticles after synthesis in reverse micelles at room temperature.
To monitor the stability of the final prepared silver particles, we measured the absorption spectra of the solution on different days. During the entire chemistry process, no passivator was added into the system. It proves that the silver nanoparticle solution prepared in such proportional reverse micelles can remain relatively stable for at least 3 months. The remnant biosurfactant in the solution is regarded as the stabilizer, which forms a steric hindrance around the particles to prevent them from aggregating greatly by electrostatic interactions.
The particle size found in this work is similar to the one obtained by Xie et al. [20], who found sizes in the range of 2–8 nm for the silver nanoparticles stabilized by the biosurfactant-rhamnolipid purchased from Jeneil Biosurfactant Co., LLC (USA) in heptane. On the other hand, Palanisamy and Raichur [21] showed nickel oxide particles of about 47 nm when the same commercial Jeneil Biosurfactant was employed under optimized pH conditions. Research involving synthetic surfactants demonstrated the synthesis of silver nanoparticles on the order of 59–70, 43–53 and 57–76 nm with the cationic cetyltrimethylammonium chloride (CTAC), the anionic sodium dodecyl sulfate (SDS) and the non-ionic Tween 80, respectively, according to the variation of concentration of solutions of these surfactants [28]. Kiran et al. [29] used a glycolipid biosurfactant produced from sponge-associated marine Brevibacterium casei MSA19 using the agro-industrial and industrial waste as substrate to synthesize silver nanoparticles. The silver nanoparticles synthesized in this study by the glycolipid were uniform and stable for 2 months.
3.2. TEM analysis
TEM analysis was carried out on the silver particles to observe the individual size and shape of the nanoparticles. TEM micrograph of sample synthesized is shown in Fig. 2, which is consistent with the absorption spectra results. A large number of smaller particles are distributed on the films, the size range of which is 1–2 nm. This indicates that the distribution of silver nanoparticles stabilized by the biosurfactant is rather uniform.
Fig. 2. Transmission Electron Micrograph of silver nanoparticles in heptane (scale = 200 nm).
The structure of the biosurfactant plays an important role in determining the morphology of the synthesized nanoparticles. These micelles are spherical in shape and favored the formation of spherical nanoparticles during synthesis.
As biosurfactants are natural surfactants derived from microbial origin composed mostly of sugar and fatty acid moieties, they have higher biodegradability, lower toxicity, and excellent biological activities. Since the biosurfactants reduce the formation of aggregates due to electrostatic force of attraction they facilitate uniform morphology and stability of nanoparticles.
Some larger particles on the films are also observed. Two possibilities are of concern. One is that the nanometer-sized water layers limit the packing of the particles in the direction perpendicular to the water layers when the particles are growing in reverse micelles, the absorption of surfactant molecules cannot totally prevent particles from aggregating and the thickness of the water layers cannot absolutely restrict the particle size due to the flexibility of the surfactant bilayers [29]. The other is that during the extraction and redispersion process many particles impact each other promoting aggregation between them.
To determine the stability of silver nanoparticles synthesized through the biosurfactant, the prepared silver particles were kept at room temperature for different day intervals. The results evidenced that nanoparticles were stable for 3 months. Control experiments without biosurfactant were included in the experimental set-up and it was observed that instead of nanoparticles, aggregated clumps were observed after 7 d. The biosurfactant would have acted as stabilization agent and prevented the formation of aggregates and favored the production and stability of the nanoparticles under the experimental conditions.
The results described here for the synthesis of silver nanoparticles from a laboratory biosurfactant produced from agro-industrial waste are promising, since the majority of reports describing the use of biosurfactants in the synthesis of nanoparticles already published in the literature make use only of commercial rhamnolipids, i.e. with a high degree of purification.
4. Concluding remarks
The present work demonstrates a simple eco-friendly method for synthesizing spherical silver nanoparticles by microemulsion technique. Silver nanoparticles were successfully synthesized using the biosurfactant from P. aeruginosa. The synthesized nanoparticles were found to be spherical in shape with uniform distribution. The experimental observation was supported by TEM analysis. The silver nanoparticles can be stabilized correspondingly for at least 3 months without passivator addition. The use of low-cost, renewable and biodegradable biosurfactants in replacement to toxic synthetic surfactants is a promising alternative for the synthesis of inorganic nanoparticles for industrial application.
This study was funded by the Foundation for the Support of Science and Technology of the State of Pernambuco (FACEPE), the Research, the National Council for Scientific and Technological Development (CNPq), the Coordination for the Improvement of Higher Level Education Personnel (CAPES) and Development Program from National Agency of Electrical Energy (ANEEL).
The authors are grateful to the laboratories of the Centre for Sciences and Technology of the Universidade Católica de Pernambuco, Brazil.
Author contribution
Proposed the theoretical frame: LAS, JEGS; Conceived and designed experiments: LAS, JEGS; Contributed reagents/materials/analysis tools: RDR, JML; Wrote the paper: LAS; Performed the experiments: CBBF, AFS, RDR, JML; Analyzed the data: LAS, JEGS.
There is no conflict of interest.
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*Corresponding author: E-mail address: leonie@unicap.br (L.A. Sarubbo).
Received 4 November 2013, Accepted 17 March 2014, Available online 2 May 2014.

redpajama_set_name: RedPajamaCommonCrawl


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var fs = require('fs');
var path = require('path');
var logger = require('logger').logger('dMap');
var async = require('async');

var maps = {};

// safely run the mapped functions, id required to be parsed idr
function condom(f, data, id, name) {
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// util to extract a common key from a raw data json object from a given service
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  return data[map[name] || name];
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// use a similar pattern for default service-level mapping values
exports.defaults = function (service, name) {
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};

exports.endpoints = function (serviceName) {
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// map all the defined fields for an entry
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// look for a guid if supported
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// one)
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  // if there's other internal types, map those too
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    try {
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      maps[service]._system = true;
    } catch (E) {
      logger.error("failed to load ", map, E);
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redpajama_set_name: RedPajamaGithub