instruction:
Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
question:
Context: Human erythrocyte spectrin is an antiparallel heterodimer comprised of a 280 kDa alpha subunit and a 246 kDa beta subunit which further associates into tetramers in the red cell membrane cytoskeleton. Lateral association of the flexible rodlike monomers involves a multiple-step process that is initiated by a high affinity association near the actin-binding end of the molecule (dimer nucleation site). In this study, recombinant alpha and beta proteins comprising two or four "spectrin type" motifs with and without adjacent, terminal nonhomologous domains were evaluated for their relative contributions to dimer initiation, and the thermodynamic properties of these heterodimer complexes were measured. Sedimentation equilibrium studies showed that in the absence of the heterologous subunit, individual recombinant proteins formed weak homodimers (K(d) > 0.3 mM). When 2-motif (alpha20-21 and beta1-2) and 4-motif (alpha18-21 and beta1-4) recombinants lacking the terminal nonhomologous domains were paired with the complementary protein, high affinity heterodimers were formed in sedimentation equilibrium analysis. Both the alpha20-21/beta1-2 complex and the alpha20-21EF/betaABD1-2 complex showed stoichiometric binding with similar binding affinities (K(d) approximately 10 nM) using isothermal titration calorimetry. The alpha20-21/beta1-2 complex showed an enthalpy of -10 kcal/mol, while the alpha20-21EF/betaABD1-2 complex showed an enthalpy of -13 kcal/mol. Pull-down assays using alpha spectrin GST fusion proteins showed strong associations between all heterodimer complexes in physiological buffer, but all heterodimer complexes were destabilized by the presence of Triton X-100 and other detergents. Complexes lacking the nonhomologous domains were destabilized to a greater extent than complexes that included the nonhomologous domains. The detergent effect appears to be responsible for the apparent essential role of the nonhomologous domains in prior reports. Taken together, our results indicate that the terminal nonhomologous domains do not contribute to dimer initiation nor are they required for formation of high affinity spectrin heterodimers in physiological buffers. 
 Question: Alpha-spectrin and beta-spectrin subunits form parallel or antiparallel heterodimers?
answer:
antiparallel


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Context: Assume that a school bus, like the one in Figure 12.2, passes by as you stand on the sidewalk. Its obvious to you that the bus is moving. It is moving relative to you and the trees across the street. But what about to the children inside the bus? They arent moving relative to each other. If they look only at the other children sitting near them, they will not appear to be moving. They may only be able to tell that the bus is moving by looking out the window and seeing you and the trees whizzing by. This example shows that how we perceive motion depends on our frame of reference. Frame of reference refers to something that is not moving with respect to an observer that can be used to detect motion. For the children on the bus, if they use other children riding the bus as their frame of reference, they do not appear to be moving. But if they use objects outside the bus as their frame of reference, they can tell they are moving. What is your frame of reference if you are standing on the sidewalk and see the bus go by? How can you tell the bus is moving? The video at the URL below illustrates other examples of how frame of reference is related to motion. MEDIA Click image to the left or use the URL below. URL: Did you ever go to a track meet like the one pictured in Figure 12.3? Running events in track include 100-meter sprints and 2000-meter races. Races are named for their distance. Distance is the length of the route between two points. The length of the route in a race is the distance between the starting and finishing lines. In a 100-meter sprint, for example, the distance is 100 meters. The SI unit for distance is the meter (1 m = 3.28 ft). Short distances may be measured in centimeters (1 cm = 0.01 m). Long distances may be measured in kilometers (1 km = 1000 m). For example, you might measure the distance a frogs tongue moves in centimeters and the distance a cheetah moves in kilometers. Maps can often be used to measure distance. Look at the map in Figure 12.4. Find Mias house and the school. You can use the map key to directly measure the distance between these two points. The distance is 2 kilometers. Measure it yourself to see if you agree. Things dont always move in straight lines like the route from Mias house to the school. Sometimes they change direction as they move. For example, the route from Mias house to the post office changes from west to north at the school (see Figure 12.4). To find the total distance of a route that changes direction, you must add up the distances traveled in each direction. From Mias house to the school, for example, the distance is 2 kilometers. From the school to the post office, the distance is 1 kilometer. Therefore, the total distance from Mias house to the post office is 3 kilometers. You Try It! Problem: What is the distance from the post office to the park in Figure 12.4? Direction is just as important as distance in describing motion. For example, if Mia told a friend how to reach the post office from her house, she couldnt just say, "go 3 kilometers." The friend might end up at the park instead of the post office. Mia would have to be more specific. She could say, "go west for 2 kilometers and then go north for 1 kilometer." When both distance and direction are considered, motion is a vector. A vector is a quantity that includes both size and direction. A vector is represented by an arrow. The length of the arrow represents distance. The way the arrow points shows direction. The red arrows in Figure 12.4 are vectors for Mias route to the school and post office. If you want to learn more about vectors, watch the videos at these URLs: (5:27) MEDIA Click image to the left or use the URL below. URL: You Try It! Problem: Draw vectors to 
 Question: When both distance and direction are considered, motion
answer:
is a vector.


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Context: This section's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (July 2015) (Learn how and when to remove this template message) The film's premise is that there is another way to heaven than adherence to the practices of the Roman Catholic Church. A secular Sin Eater can remove all taint of sin, no matter how foul, from the soul just before death. The purified soul can then ascend into heaven. The Roman Catholic Church, according to the film, considers this heresy. Heath Ledger plays an unhappy and disillusioned priest, Alex Bernier, a member of a fictitious religious order The Carolingians which specializes in fighting demons and other hell spawn. Father Dominic, the head of the Carolingians, has died in Rome under suspicious circumstances and Alex leaves the United States to investigate. In Rome, Alex visits the morgue and sees strange markings on Dominic's corpse. After some investigation, he comes across a book that explains the markings as being the sign of a Sin Eater's work. He heads to the Vatican, where an official tells him that Sin Eaters don't exist and that Dominic may not be buried on sacred ground because he had been excommunicated for his beliefs. Alex, moving ever farther from his vocation, defies his superiors and secretly reads a holy service over the body and buries Dominic in the Carolingian cemetery (the service takes place off screen but is referred to later). Thomas Garrett, another Carolingian (there seem to have only been a total of three including Dominic), arrives in Rome to help investigate Dominic's death. Early in the film we meet Mara Williams, an artist Alex once exorcised, who has escaped from a mental hospital and come to Alex at his church in the USA because she has a feeling that something terrible is going to happen to him. The police come looking for her, but Alex lies and denies that he's seen her and through this exchange we learn that Mara was in the hospital because she had tried to kill Alex during the exorcism. Mara goes to Rome with Alex after promising that she won't try to kill him again. Cardinal Driscoll (Peter Weller), who is introduced at the beginning of the film and who is tipped to be the next Pope, arrives in Rome from the USA and gives Alex a special dagger. According to a fragment of parchment Alex and Thomas find among Dominic's books, the dagger is to be plunged into the Sin Eater while reciting a text in Aramaic. Alex and Thomas take these instructions to mean that the dagger and incantation will kill the Sin Eater and they begin hunting for the Sin Eater and the remainder of the parchment instructions. Thomas leads Alex to a nightclub where they are taken to the underground base of operations of a masked man called Chirac, the 'Black Pope.' The Black Pope owes a favor to Thomas and Alex asks where to find the Sin Eater. The Black Pope then hangs three people and tells Alex to ask his question of the dying men who can see what the living cannot. One of the dying tells Alex a riddle that leads to a rendezvous with the Sin Eater. On the way out of the Black Pope's headquarters, demons attack and injure Thomas, but Alex saves him and gets him to a hospital. Alex leaves Thomas in the hospital and meets the Sin Eater, William Eden, at St. Peter's Cathedral who explains that he has been a Sin Eater for centuries, taking over for an earlier Sin Eater (a Carolingian priest) who ate the sins of Eden's brother. Eden is very charismatic and talks with Alex about the priest's desires, and Alex admits he wants Mara. He then goes and presumably tells Mara this, and they make love. Afterward, Alex leaves Mara asleep and goes to Eden, who tells Alex that he is tired and ready to die and asks Alex to take his place. Alex has the dagger with him, but is curious and so doesn't use it to kill Eden. Instead, he assists Eden with a sin eating 
 Question: What was the name of the old comrade Alex enlisted help from?
answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
mara


