Sunday, January 26, 2020

Method Development for Protein Detection

Method Development for Protein Detection Binding-induced and label-free colorimetric method for protein detection based on binding-induced DNA hybridization and DNAzymebased signal amplification INTRODUCTION In diagnosing the early stage of a disease or pathological condition, proteins, especially those associated with cancers, are of great importance because they are the molecular machinery of life.[BB2013-AM-3, 1,2] Enzyme-linked immunosorbent assay (ELISA) is the most commonly used method for protein detection.[PD-3,1,2] Unfortunately, this antibody-based assay requires a long incubation periods and long assay times with the involvement of multiple washing steps.[PD-5,1,2] Additionally, it is faced with the challenges of insufficient sensitivity and limited dynamic range.[PD-4, 5,6,7] As an alternative to the antibody-based assay, aptamer-based assays have gained tremendous attention recently.[PD-4,9-11] Aptamers are single stranded DNA or RNA oligonucleotides selected from random sequence nucleic acid libraries through an in vitro selection process termed systematic evolution of ligands by exponential enrichment (SELEX).[PD-6,4-6] They possess high affinity and good selectivity for s mall molecules, proteins or other targets.[BB-11,20-22] Compared to antibodies, aptamers exhibit obvious advantages including a better stability for long-term storage, a rapider preparation by chemical synthesis in large quantity, and the flexible modification with a variety of functional groups.[PD-4, BB-11,23,24] Some aptamer-based amplified detection assays for protein have been developed in the past two decades, such as the polymerase chain reaction (PCR), rolling circle amplification (RCA), strand displacement amplification (SDA) and ligase chain reaction (LCR). [BB-AM-3] Although these amplified assays greatly enhance the sensitivity of protein detection, they are usually time-consuming and too complicated. Therefore, the amplified detection of protein is still challenging in bioanalytical chemistry.[BB2013-AM-3] Deoxyribozymes (DNAzymes) are artificial nucleic acids, which are isolated from in vitro selection. [DM-5] Similar to traditional protein enzymes, they exhibit high catalytic hydrolytic toward specific substrates, while they possess higher thermal stability that can be denatured and renatured formanycycles without losing catalytic activities.[DM-4] This obvious advantage makes DNAzymes ideal biocatalysts for achieving signal amplification in biological applications.[DM-4] An important development in the DNAzyme field is the discovery of the G-quadruplex DNAzyme.[DM-9,9] The G-quadruplex sequences can associate with a cofactor, hemin, to form peroxidase-mimicking DNAzymes to catalyze the H2O2-mediated oxidation of 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to a green-colored product ABTS†¢Ã¢Ë†â€™ or enhance the chemiluminescence of the luminol-H2O2 system.[DM-6,25, DM-5,44] With this main advantage, G-quadruplex DNAzyme has been employed to develop many colorime tric, chemiluminescent or fluorescent sensing platforms for the detection of proteins, DNA and other biomolecules.[DM-9,14,DM-2,34-37] Recently, Willners group reported an enzyme-free amplified detection platform based on the hemin/G-quadruplex horseradish peroxidase (HRP)-mimicking DNAzyme.[AC2012-2] This strategy is quite successful, while the target detection is limited to DNA, and the detection of protein represents another challenge. In this work, taking the advantages of the high selectivity and affinity of aptamers and the HRP-mimicking DNAzyme amplification strategy, we designed a new binding-induced and label-free ultrasensitive colorimetric method for amplified detection of protein. As a proof of principle, human ÃŽ ±-thrombin and its two aptamers, Apt29 and Apt15, are used. In this sensing system, Apt29 and Apt15 are integrated into the proximity probes as recognition elements for the thrombin. These two proximity probes hybridize with each other stably only when both of them bind to the thrombin simultaneously.[BB2013-AM-3] The binding-induced hybridization duplex triggers an autonomous cross-opening of the two functional hairpin structures. And this leads to the formation of a variety of hemin/G-quadruplex DNAzymes. The DNAzymes catalyze the oxidation of ABTS, generating a green colorimetric signal, which can be monitored simply by a spectrophotometer. [DM-3,29,30] This binding-induced and DNAzyme-based s ignal amplified method has a great potential for protein detection. [BB2013-AM-3] In addition, since various recognition elements might be fused, this method can be further extended to sensitive detection of other proteins.[DM-4] EXPERIMENTAL SCETION Materials and Reagents. All DNA oligonucleotides were purchased from Genscript (Jiangsu, China). The oligonucleotides were PAGE-purified and diluted in pH 7.4, 20 mM Tris-HCl buffer solution (containing 100 mM NaCl, 20 mM KCl, and 2 mM MgCl2) to give stock solutions of 100 ÃŽ ¼M. Before use, two hairpin structures were heated to 95à ¢Ã¢â‚¬Å¾Ã†â€™ for 5 min, and slowly cooled down to room temperature. Human ÃŽ ±-thrombin (Tb), bovine serum albumin (BSA), and human serum albumin (HSA) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Hemin, [tris(hydroxymethy-l)aminomethane] (Tris), 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid sodium salt (HEPES), 2,2-azino-bis(3-ethylbenzothiozoline-6-sulfonic acid) (ABTS), and H2O2 were purchased from Aladdin Reagents (Shanghai, China). A hemin stock solution (1 mM) was prepared in dimethyl sulfoxide (DMSO) and stored in the dark at −20  °C. All other chemicals were of analytical grade and were used without further purification. All solutions were prepa red using double-distilled water, which was obtained through a Milli-Q purification system (Billerica, MA, USA). Absorbance Measurements. Absorbance measurements were performed under room temperature using a TU-1901 UV−visible spectrophotometer (Beijing Purkinje General Instrument Co, Ltd., China). Kinetic data were recorded at the wavelength of 420 nm every 5 s during the first 5 min of the reaction. The absorption spectra of the solution was measured in the wavelength range from 390 to 490 nm. Procedure for Thrombin Assay. The experiments were performed in 50 ÃŽ ¼L of Tris-HCl buffer (20 mM Tris-HCl, pH = 7.4, 100 mM NaCl, 20 mM KCl, 1 mM MgCl2) containing 200 nM P1, 200 nM P2 and varying concentrations of Tb. The mixture was first incubated for 30 min at room temperature to allow complete binding. Next, 25 ÃŽ ¼L of 2 ÃŽ ¼M H1 and 25 ÃŽ ¼L of 2 ÃŽ ¼M H2 were added and incubated for 6 h at room temperature. Then, 20 ÃŽ ¼L of 2 ÃŽ ¼M hemin and 240 ÃŽ ¼L of HEPES buffer (25 mM HEPES, pH= 7.4, 200 mM NaCl, 20 mM KCl, 0.05% Triton X-100, 1% DMSO) were added, and allowed to incubate for 1 h at room temperature. Finally, 30 ÃŽ ¼L of ABTS and 10 ÃŽ ¼L of H2O2 were added to the mixture to give the final concentrations of 2 mM and 2 mM, respectively. The resulting samples were tested with a UV−vis spectrometer. RESULT AND DISCUSSION Design strategy for human ÃŽ ±-thrombin detection The sequences of the oligonucleotides used in this work were listed in Table 1. It consists of two proximity probes (P1 and P2) and two hairpin structures (H1 and H2). Both proximity probes P1 and P2 consist of four domains. Domain I includes two different thrombin aptamers, Apt29 (29 mer) and Apt15 (15 mer). The Apt29, orange domain of P1, binds to the heparin-binding site and the Apt15, skyblue domain of P2, binds to the fibrinogen-binding site of thrombin, resulting in proximity. Domain II (black) consists of a poly-T sequence that is designed to reduce the effect of steric hindrance induced by thrombin. Domain III (pink) is designed to have only 6 complementary bases, so that two proximity probes P1 and P2 cannot form a stable duplex without the target protein at room temperature. Domain IV (blue) is the key domain for binding-induced DNAzyme-assised signal amplification. By using two functional hairpin structures, the recognition of domain IV could trigger-on the hybridization c hain reaction that led to DNAzyme chains consists of the hemin/G-quadruplex HRP-mimicking DNAzyme. Hairpin structure H1 is functionalized at its 5 end with three-fourths of the G-quadruplex sequence, domain V (green), which is linked to the programmed sequences VIII (red) and VII (blue). One-fourth of the G-quadruplex sequence, domain VI (green), is extended at the 3 end of the hairpin H1. Hairpin structure H2 is functionalized at its 5 and 3 ends with one-fourth of the G-quadruplex (domain VI) and three-fourths of the G-quadruplex (domain V) sequence, respectively. Programmed sequences of domains VII and VIII in hairpin H2 are complementary to domains VII and VIII in hairpin H1, respectively. Both four domains in hairpin H1 and H2 are incorporated into a stable hairpin configuration in an initially locked format by hybridizing with their partially complementary sequences. It is noteworthy that sequence V is partially hybridized with domain VII in hairpin H1 or VIII in hairpin H2, w hich prevents the self-assembly of the active hemin/G-quadruplex DNAzyme. Principle of binding-induced DNAzyme-assisted amplification strategy for human ÃŽ ±-thrombin detection The working principle of human ÃŽ ±-thrombin detection is illustrated in Scheme 1. In the absence of thrombin, domain III in P1 and domain III in P2 will not associate since the complementary sequences (6 nt) are too short to promote efficient hybridization. When the target thrombin is introduced into the system, domain I in P1 and P2 bind to the protein simultaneously, resulting in domain III and III sufficiently close and to hybridize to each other to form a stable P1-Tb-P2 duplex, step 1. [BB2013-AM-3] Once the P1-Tb-P2 duplex forms, it associates with the stem region of H1, domain VII, leading to an opening of H1. This opening of H1 results in the release of the single-stranded domain VIII and the conserved three-fourths of the G-quadruplex (domain V), step 2. The released domain VIII then hybridizes with domain VIII of the stem in H2, and opens H2 using the strand displacement principle, step3. Subsequently, the liberated domain VII in H2 cross-hybridizes with H1 by hybridizatio n of domain VII to domain VII in H1, resulting in two G-quadruplex subunits (domain V and VI) sufficiently close and to self-assemble into a G-quadruplex structure, step 4. [AC2012-4] In the process of this autonomous cross-opening of H2 and H1, strand displacement can be repeated continuously, generating numerous G-quadruplex structures. In the presence of hemin, the resulting catalytic hemin/G-quadruplex peroxidase-mimicking DNAzymes catalyze the H2O2-mediated oxidation of the colorless ABTS2− to green-colored ABTS†¢Ã¢Ë†â€™. Detection of thrombin in human serum To further demonstrate the feasibility of the proposed method in real bioenviroments, we performed the detection of thrombin in human serum. [AC2013-4] Three concentrations of thrombin (10 pM, 100 pM, and 1000 pM) were spiked into 10-fold diluted human serum. [ZK-CC-1] Figure 4 shows the time-dependent absorbance changes of ABTS†¢Ã¢Ë†â€™ in response to different concentrations of thrombin. [AC2014-6] In logarithmic scales, the absorbance value exhibits a linear correlation with thrombin concentration over a range of 3 orders of magnitude from 10 pM to 1000 pM (inset of Figure 4B). [AC2012-12] The result indicated the potentiality of the proposed method for protein detection in real biological samples. [AC2013-4] Conclusions In conclusion, we have developed a binding-induced and label-free colorimetric method for protein detection based on binding-induced DNA hybridization and DNAzyme-assisted signal amplification. This method does not require any modification of DNA and involve any protein enzyme, which makes it technically label-free, enzyme-free and very cost-effective. Furthermore, the present approach uses a simple separation-free procedure in which the assay is conducted in a homogeneous solution.[AC2014-3] In addition, due to the excellent specificity of two proximity probes to the thrombin and the ingenious design of two hairpin structures,[AC-EA-2] this method exhibits a high sensitivity for thrombin detection, with a low detection limit of 2.5 pM. More importantly, this method can be extended to sensitive detection of other proteins by simple changing the aptamer sequences of the two proximity probes. To sum up, this simple and cost-effective colorimetric signal amplified method has great poten tial to be used as a universal tool for ultrasensitive analysis of thrombin or other proteins in serum and supply valuable information for biomedical research and clinical diagnosis.[ZK-CC-1]

Saturday, January 18, 2020

Composed upon Westminster Bridge and The World is too much with us

William Wordsworth, poet and writer, born on April 7th, 1770 in a small Cumberland village named Cochermouth, located on the northern edge of the Lake District. He attended infant school in the small town of Hawkshead, located in one of the most beautiful regions of the Lake District. Wordsworth remained at Hawkshead until the age of 16. There were some long and deeply impressive rumples through the country, which affected his poetry greatly. You will realize that he loves nature and had a deep loyalty to Britain, even though he lived in France and was married to a French woman. The two poems I will be discussing are; â€Å"The World is too much with us† and â€Å"Composed upon Westminster Bridge†. It is interesting to notice that both of these poems take on a Petrarchan sonnet form. The form of a sonnet consists of an octave (first 8 lines) and a sestate (last 6 lines). This gives us a total of 14 lines. However in â€Å"The World is too much with us† a unique and significant form is taken on; Wordsworth gives the octave 8 and a half lines while the sestate has only 5 and a half. Wordsworth uses the octave for the exposition or the theme and the sestate for the conclusion. â€Å"The World is too much with us† embodies one of the central ideas of the Romantic Movement in poetry, of which Wordsworth was a founder – that in our daily life, especially living in towns, we have lost touch with the renewing powers of nature. â€Å"Composed upon Westminster Bridge† is a magnificent sonnet, which shows Wordsworth appreciating and indeed demonstrating the beauty of a great city – though perhaps it is characteristic of his love for solitude, and is set in the early morning, when there is no bustle and noise. Throughout both sonnets Wordsworth cleverly employs the use of semicolons, colons, comma or just a full stop. His reasons for this is to make us pause, reflect and get the true meaning of the line we have just read. In the first two lines of â€Å"The World is too much with us† – The World is too much with us; late and soon Getting and spending, we lay waste our powers: Wordsworth uses both the semicolon and the colon and intends us to think â€Å"what world?† â€Å"which power?† he gets across that we are being engulfed in the materialistic world and have a lack of concern for nature, thus we take nature for granted and we waste our natural powers. In the corresponding lines of â€Å"Composed upon Westminster Bridge† – Earth has not anything to show more fair: Dull would he be of soal who could pass by A sight so touching in its majesty: Wordsworth utilizes a number of ploys to grab our attention. The opening line is a bold statement meaning he has not ever seen a better sight. The use of the word â€Å"earth† suggests the supreme quality of such beauty. He uses the words â€Å"earth†, â€Å"anything† and â€Å"fair† to indicate the entire world. In the second line syntax is put to use; â€Å"dull would he be of soul† as opposed to â€Å"he would be dull of soul†. This is for extra emphasis on the word â€Å"dull†. He also uses enjambment by allowing lines 2 and 3 to flow together as 1; this helps to stress ‘a sight so touching'. The repetition of the letter s sound helps to convey the ‘breathless' sense of admiration. Touching is a word that we can all relate to whereas majesty shows the importance of nature and how much he was startled by this view. In the next two lines of â€Å"The World is too much with us† – â€Å"Little we see in Nature that is ours; We have given our hearts away, a sordid boon!† Here Wordsworth gives nature a capital letter. This is the first indication in the poem of what it is about. Syntax again is used where he could have simply written â€Å"we see little in nature that is ours†, which means we don't recognise nature as being part of ours. In line two, the poet says â€Å"we have given our hearts away†, our heart is associated with love and without it he is implying we do not appreciate nature in the manner we should. A sordid boon is a phrase used to convey the meaning of a gift of no value. This hints that we no longer value our love by living in the materialistic world. Wordsworth uses personification in line four of â€Å"Composed upon Westminster Bridge†. A simile is also implied for further understanding. â€Å"This City now doth, like a garment, wear The beauty of the morning; silent, bare† Garment suggests a comfortable easy fit yet the world is more grand than say, clothing, and the beauty of the scene is enhanced by implications of resplendent finery. Another capital letter is used in the middle of the sentence on the word city. This shows the importance and beauty of the city. The two lines mean that the city now wears the beauty of the morning; again Wordsworth shows us his love and passion for nature. In the corresponding lines of â€Å"The World is too much with us† there is the same punctuation and language affects – â€Å"This Sea that bears her bosom to the moon; The winds that will be howling at all hours, And are up-gathered now like sleeping flowers; Again to show the importance of nature Wordsworth uses a capital letter on sea, which is most of our natural world today. Personification is used on these same lines – â€Å"the sea that bears ‘HER' bosom to the moon† and â€Å"the winds that will be ‘HOWLING' at all hours†. â€Å"Like sleeping flowers† is the simile implied to show the calming after the storm. The octave in â€Å"Composed upon Westminster Bridge† ends with: – â€Å"Open unto the fields, and to the sky; All bright and all glittering in the smokeless air.† You could almost say these statements are incorrect, but remember it was the 1800's when this sonnet was composed. When Wordsworth stood upon this bridge he could see everlasting green fields, surrounding London, that lead right to the horizon. Open is a word that could mean anything but in this poem it means that there is a light open feeling to the atmosphere. â€Å"Smokeless† – still, pure, unpolluted. Perhaps this reminds us of how the scene will change once days of smoky industry begin. â€Å"For this, for everything, we are out of tune; It moves us not.† These are the last one and a half lines of the octave in â€Å"The World is too much with us†. Wordsworth suggests here that we are out of tune. Thus hinting we are not in harmony with nature. This again shows the difference of tone. In â€Å"composed upon Westminster Bridge† the tone is a hushed, almost breathless admiration. He was surprised by sudden vision of splendor and became more emotional whereas he recognizes the materialistic living in â€Å"The World is too much with us†. The sestet of â€Å"The World is too much with us† opens with â€Å"Great God†. Wordsworth recognises God's great power of nature but he would also rather be a Pagan because Pagan's appreciated nature. He wants to see glimpses to make him less sad and a glimpse would keep the suspense and make him more aloof. Proteus and Triton are Greek Gods. Proteus: Greek sea God and Triton: one of a race of minor sea – Gods in Greek mythology, with a mans form but the tail of a fish, often depicted as carrying a shell – trumpet. In the sestet of â€Å"composed upon Westminster Bridge† Wordsworth seems very happy with the view of London city with the sun rising. He says such things as: â€Å"Never did the sun more beautifully steep†, and â€Å"Ne'er saw I, never felt, a calm so deep!† which is another cleaver use of syntax. This is a change from â€Å"The World is too much with us† as in that sonnet the wonderful natural scenery in which he was writing made him sad to think about how people don't appreciate it anymore. â€Å"Dear God† is also used in â€Å"composed upon Westminster Bridge†. This is maybe his prayer to God to keep nature so beautiful whereas in â€Å"The World is too much with us†, he used â€Å"Great God† as to say WAKE UP! We (the readers) can visualize and relate to the wonderful scenery Wordsworth describes effectively, with language and punctuation to convey his meaning.

Friday, January 10, 2020

Why Absolutely Everyone Is Talking About Ap Language 2013 Synthesis Essay Samples

Why Absolutely Everyone Is Talking About Ap Language 2013 Synthesis Essay Samples Rehashing exactly the same ideas does not bring in viewers in the exact way that being a modest controversial does. Due to such things the author will have the ability to write several standard thesis and construct the rest of writings on them. A writer is provided a prompt to study. He proves her words with the help of recent studies. What Is So Fascinating About Ap Language 2013 Synthesis Essay Samples? Before generating the info from the prompt sources you ought to go through a research stage during which you search for, investigate and decide on the facts that go with the topic of your essay. Make sure you choose at least two sources if your task is to make a synthesis paper. It is crucial to use the sources before your to inform your FRQ response. The in-depth study of the health condition has resulted in the visual appeal of a new therapy. Alcohol needs to be made illegal once again alcohol is the worst drug, yet alcohol is the simplest drug to get because it's a legal substance the use of alcohol. What Everybody Dislikes About Ap Language 2013 Synthesis Essay Samples and Why For a normal student a synthesis paper may sound quite troubling, as it isn't a typical endeavor to finish. Writing a synthesis paper isn't such a huge challenge as it may appear at the start. So, keep reading for everything you will need to know to knock your synthesis essay from the park! If it is all about figuring out how to compose an AP English synthesis essay, it is necessary to open the official AP website with the present requirements and study the grading rubric to comprehend what things to concentrate on. The variety of body paragraphs depends upon the number of arguments you will discuss. Hence the body needs more than 1 paragraph. Terrific synthesis topics are those that refer to general understanding, for instance, Yoga Develops You Both Physically and Mentally. The Argument About Ap Language 2013 Synthesis Essay Samples When you read each document, it is a very good notion to have a minute to label the documents. You also have to fully grasp how to format it correctly. In line with your task, you might be required to go for the major text. Based on your assignment, you may have to pick a main text. Ap Language 2013 Synthesis Essay Samples Secrets You should consider it closely to reveal your argument from a more powerful perspective. In fact, analysis of the given content is an important point in the whole synthesis essay writing. Following your thesis statement, you're want to mention your supporting reasons. Rhetorical analysis is about the author and his targets. Choose a topic for which it would be simple to write because many arguments as needed. Guided by means of a set of instructions, you should support your ideas in favor of the specific topic. Your topic might seem weak if it's not clear enough. For instance, it is associated with vegetarianism and the prompt gives you 7 different sources to analyze. Want to Know More About Ap Language 2013 Synthesis Essay Samples? You have to realize that synthesis doesn't imply summarizing. Since you can see, it isn't that simple to compose a synthesis essay. Now once you know what a synthesis essay is that can begin working on it! A synthesis essay is about combination. The Basics of Ap Language 2013 Synthesis Essay Samples That You Can Benefit From Starting Immediately It is very hard to influence the point of view of a person who's connected to a topic through a potent feeling. The close reading is the procedure which follows any great research. Regardless, keep in mind that you're arguing so presenting information supporting only a single side isn't sufficient enough! There is not sufficient info to create a la st decision. The New Fuss About Ap Language 2013 Synthesis Essay Samples It is insufficient to deliver an overview of each observed text. The examples may also be downloaded via the download hyperlink button beneath the sample so as to find a close look. Frequently, it includes a text which you should analyze. Cross out the texts you don't mean to use. If you're writing your essay with some too brief deadline on an exam, you will need to stress on your argument in each paragraph. Make sure that you leave a highly effective conclusion when writing your essay. The task consists of a sample text an author should analyze. A significant question takes a critical answer. It's best utilized whenever you have the view of the reader accessible. Convince your reader that you're right. According to academic requirements, the author should use an immediate quote. The student doesn't consist of information that the reader can't get from reading the document.

Wednesday, January 1, 2020

Struggles and Tensions in Death of a Salesman by Arthur...

In drama, struggles and tensions within the lives of characters and the situations they face are important for the building of the plot and maintaining the attention of the audience. In Death of a Salesman by Arthur Miller and Fences by August Wilson, the main characters of the plays face struggles which move the plot along, while adding anticipation and excitement. Willy and Troy face struggles internally and externally with society. Willy struggles with failing business, while Troy struggles with feelings of being segregated form society. Both men also face conflicts with their marriages and with their relationships with their sons. These struggles are evident throughout the entire play and are enhanced by many examples.†¦show more content†¦His whole life has been built around his job and building a financially stable household. Now he struggles to keep a steady income. Willy understands societys emphasis on the importance of a profitable worker. Linda says, A smal l man can be just as exhausted as a great man. He works for a company for thirty-six years this March, opens up unheard-of territories to their trademark, and now in his old age they take his salary away (Miller 1713). Willy works his whole life with a stable job, which is suddenly jeopardized. Willy struggles internally with feelings of worthlessness because of his job situation. In his interview with the Paris Review, Miller says Willy believes a man who experiences failure in society and in business has no right to live (2035). In her work titled Marxism and the Early Plays of Aurther Miller, Helge Nilsen states, Human beings are sacrificed to economic interests in ways that are not only immoral, but even criminal in nature (2038). Society places a huge emphasis on a persons economic status, and Willy begins to struggle with this immensely. Willy falls victim by the free play of economic forces, and this is a main conflict theme in the play (Nilsen 2039). In Fences, the ch aracter Troy also faces conflict with society. His conflicts are not necessarily based on economic problems, but rather on feelings of injustice brought on by the white race. Troy believes the white man is out to destroy the blackShow MoreRelatedDeath of a Salesman by Arthur Miller811 Words   |  3 PagesIn the plays Fences by August Wilson and Death of a Salesman by Arthur Miller, two types of father-son relationships are shown. The difference in the relationship causes each son from the play to result in a different way of life. Troy Maxson, from Fences, has an unfulfilled dream which causes a jealousy of his son, and a dominant relationship. This causes tension and bitterness between them and continues to affect his son Cory is more ways than one. Willy, from Death of a Salesman, is always expectingRead MoreDeveloping Management Skills404131 Words   |  1617 Pagesmanagement school also reported: I can’t believe it. I went for my second interview with a company last week, and I spent the first half-day participating in simulation exercises with ten other job candidates. They videotaped me playing the role of a salesman handling an irate customer, a new director of personnel putting down a revolt by the â€Å"old guard,† and a plant manager trying to convince people of the need to install a radically new production process. Boy, was I unprepared for that! The message