Purines are complementary only with pyrimidines: pyrimidine-pyrimidine pairings are energetically unfavorable because the molecules are too far apart for hydrogen bonding to be established ; purine-purine pairings are energetically unfavorable because the molecules are too close, leading to overlap repulsion.

As a short-hand, the nucleotides that form the rungs of the ladder in the DNA double-helix are often referred to by biologists, as their base pair identity such as adenine ( A ), see: Category: Purines and: Category: Pyrimidines.

In normal spiral DNA the bases form pairs between the two strands: A with T and C with G. Purines pair with pyrimidines mainly for dimensional reasons-only this combination fits the constant width geometry of the DNA spiral.

In the genetic code, it is common for a single amino acid to be specified by all four third-position possibilities, or at least by both Pyrimidines and Purines ; for example, the amino acid glycine is coded for by the codon sequences GGU, GGC, GGA, and GGG.

Of greater importance, however, is the content of those programs, which have had and are having enormous consequences for the American people.

These are not, however, differences in federal structure.

There are, however, some wonderful chapters at the beginning of the second part, concerning the reactions of the Swedes in adversity.

Even on the fictional level, however, the contradictions which give rise to the mystery story are not fully resolved.

Despite this danger, however, we are informed on every hand that ideas, not machines, are our finest tools ; ;

We are reminded, however, that freedom of thought and discussion, the unfettered exchange of ideas, is basic under our form of government.

But however we come, finally, to explain and account for the present, the truth we are trying to expose, right now, is that the makers of constitutions and the designers of institutions find it difficult if not impossible to anticipate the behavior of the host of all their enterprises.

But there are, however, several features of Aristotle's approach which open the way for the moral measure of literature.

But now he knows `` that an intellectual is not only a man to whom books are necessary, he is any man whose reasoning, however elementary it may be, affects and directs his life ''.

It is not clear, however, whether they are thinking of all movable property or only of boats, trailers, aircraft or certain other types of personal property whose assessment would be advantageous to their particular towns.

Avocados, however, are very rich in nutrients.

however, he will have a clearer understanding of what he is doing and the chances are he will be more successful if he understands the few formulas that apply to rodding.

Even when they are finished, however, the contrast will remain, for Istanbul is the only city in the world that is built upon two continents.

Part of this headquarters staff, however, are engineering managers who work between divisional chief engineers and headquarters management.

Very small particles, however, in a size range of 1 to 4 microns in diameter are capable of passing these impinging barriers and entering the alveolar bed of the lungs.

It must be remembered, however, that there are many agents for which there is no solid immunity and a partial or low-grade immunity may be broken by an appropriate dose of agent.

The antithyroid drugs of the thiouracil type, however, are not antagonised by such means.

Adverbial second complements, however, are likely not to have dominant stress when they terminate sentences.

The phonemic systems which must support these morphophonemic systems, however, are very different.

At this time, however, there are signs that increased availability of mortgage credit will not act with the usual speed to stimulate a sharp rise in residential construction.

As we have noted, however, we are abstracting from changes in all determinants of this level except for changes in the wage rate.

To insure uniformity in the meaning of national law, however, state interpretations are subject to Supreme Court review.

But the practice is likely to be misleading, since it may seem to support a conclusion that, as long as the revenues from any class of service cover the imputed operating expenses plus some return on capital investment, however low, the rates of charge for this service are compensatory.

What we have seen in this chapter, we have seen only dimly, and yet the results, however general, are worth the search.

Even in its present form, however, the first part of Malraux's unrecoverable novel is among the greatest works of mid-twentieth century literature ; ;

For the most part, however, the new version is contemporary and, as such, should be the means for many to attain a clearer comprehension of the meaning of those words recorded so many hundreds of years ago by the first followers of Christ.

As it has turned out, however, the excessive enthusiasm in the first instance and the loss of hope in the second were both wrong responses.

There would, however, be a variety of other skills -- medical, agricultural, engineering -- which would be called for in the first year through the private agency programs and through the provision of technician helpers to existing development projects.

It will not, however, be used for symbolic assignment until all other index words or electronic switches have been assigned for the first time.

After finding that its coasts led nowhere, however, he turned north again, toward the main, ice-filled passageway -- and the crew, at first uneasy, then frightened, rebelled.

The truth is, however, that when Mel Chandler first reported to the regiment the only steed he had ever ridden was a swivel chair and the only weapon he had ever wielded was a pencil.

Radio broadcasts, however -- now that even plain people could afford `` loud speakers '' on their sets -- held old fans to the major-league races and attracted new ones, chiefly women, who through what the philosopher called the ineluctable modality of audition, became first inured, then attracted, then addicted to the long afternoon recitals of the doings in some distant baseball park.

It was Porter, however, who produced the very first movie whose name has lived on through the half century of film history that has since ensued.

however, the first belief stood for entire revision with a new third point added to the list.

The meeting will, however, afford a timely and convenient opportunity for the first personal contact between them and a general exchange of views on the major issues which affect the relationships between the two countries ''.

In one thing the higher critics, like the modernists, however, overreached themselves, in claiming that the Gospel of John was not written in John's time but well after the first century, perhaps as late as 150 A.D..

The first substantial text in Japanese, however, is the Kojiki, which dates from 712 AD.

To Arminians, however, both initial salvation and eternal security are " by faith alone "; hence " by faith first to last ".

The machine was, however, the first to implement three critical ideas that are still part of every modern computer:

Throughout European history, philosophers such as Aristotle and Thomas Aquinas, among others, contemplated the possibility that souls exist in animals, plants, and people ; however, the currently accepted definition of animism was only developed in the 19th century by Sir Edward Tylor, who created it as " one of anthropology's earliest concepts, if not the first ".

Little is known of his life, however it is clear that Alan entered the schools no earlier than the late 1140s ; first attending the school at Paris, and then at Chartres.

No larger settlements, however, have been found to have existed in this remote rural area, located at least 15 km from the nearest road even in Roman times, up to the early medieval period when the place is mentioned as a king's mansion for the first time, not long before Charlemagne became ruler of the Germanic Franks.

This novel is the first of a series of novels primarily about the life and times of Robert the Bruce however it covers Alexander III and the circumstances surrounding his death in some detail.

Amos, however, is the first prophet whose name also serves as the title of the corresponding biblical book in which his story is found.

What is typical for his entire career, however, is a concern for design as a Gesamtkunstwerk, a total work of art ; whereby he-together with his first wife Aino Aalto-would design not just the building, but give special treatments to the interior surfaces and design furniture, lamps, and furnishings and glassware.

According to some traditional interpretations of the Book of Exodus, Book of Numbers, and the Letter to the Hebrews the Ark also contained Aaron's rod, a jar of manna and the first Torah scroll as written by Moses ; however, the first of the Books of Kings says that at the time of king Solomon, the Ark contained only the two Tablets of the Law.

Alan Cameron, however, argues that it should be interpreted as referring to Plato, and that when Proclus writes that " we must bear in mind concerning this whole feat of the Athenians, that it is neither a mere myth nor unadorned history, although some take it as history and others as myth ", he is treating " Crantor's view as mere personal opinion, nothing more ; in fact he first quotes and then dismisses it as representing one of the two unacceptable extremes ".

:: 1973, 1995 *( Ajax also won in 1972, however, UEFA only sanctioned the UEFA Super Cup for the first time in 1973 so the 1972 edition was an unofficial one.