Erratum

The article "Back to the energy crisis" by Mark Crawford (News & Comment, 6 Feb., p. 626) overstated American imports of petroleum and petroleum products for the years 1977 and 1985. Imports in 1977 averaged 8.8 million barrels per day as opposed to 8807 million barrels as stated. By 1985 imports had fallen to 5.07 (rounded) million barrels per day, not 5067 million barrels daily. The United States' use of petroleum-not foreign consumption as stated in the article-is projected to hit 17.7 million barrels per day in 1995. U.S. imports could then reach 9.8 million barrels a day.     

Structural evidence for evolution of the beta/alpha barrel scaffold by gene duplication and fusion

The atomic structures of two proteins in the histidine biosynthesis pathway consist of beta/alpha barrels with a twofold repeat pattern. It is likely that these proteins evolved by twofold gene duplication and gene fusion from a common half-barrel ancestor. These ancestral domains are not visible as independent domains in the extant proteins but can be inferred from a combination of sequence and structural analysis. The detection of subdomain structures may be useful in efforts to search genome sequences for functionally and structurally related proteins.     

Somatosensory cortex: structural alterations following early injury to sense organs

In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels." Each barrel is related to one sensory vibrissa on the muzzle. Individual vibrissae were carefully injured at birth; 12 to 43 days later, the corresponding barrels proved to be absent. Evidently the sensory periphery has an important influence on the structure of the somatosensory cortex.     

Letter to the editor

Morris Muskat (Letters, 6 June, p. 973) refers to "the only certain new net [oil] supplies we can count on by 1985 ... when the Alaskan pipeline is operating." The amount cited should have been "1 to 2 million barrels per day."     

National strategic petroleum reserve

The Strategic Petroleum Reserve is intended to reduce the vulnerability of the United States to interruptions in the oil supply from foreign sources. Storage for 248 million barrels of crude oil in salt caverns and mines, with equipment for pumping and distribution, was constructed and operationally tested in a 4-year period. Its present inventory is the largest known crude oil reserve in the world. Facilities for expanding the reserve's capacity by another 290 million barrels are being developed by solution-mining in salt domes.     

宠物犬胃内异物诊断与治疗

本病是宠物犬误食了难以消化的异物,如石块、大骨块、金属物件、丝袜、塑料及毛球等物体,不能被胃液所消化,又不能通过呕吐或经肠道排出体外,成为胃内异物,造成胃功能紊乱,继发慢性胃炎等疾病。临床上以长期食量减少、呕吐、消瘦为特征。多见于幼犬和小型品种的犬。     

橡木桶贮赤霞珠干红葡萄酒主要理化指标变化的研究

旨在通过定期测定酒精发酵和苹乳发酵结束后的葡萄酒在橡木桶中的总酸、挥发酸、游离硫、丹宁、p H、色度、色调等理化指标,研究橡木桶对葡萄酒品质的影响。优质干红葡萄酒一般都要经过橡木桶储藏陈酿,而橡木桶究竟如何提高葡萄酒品质,表现在哪些方面,除了感官品尝外,理化指标可以作为了解其作用的辅助参考。本文通过8个月的橡木桶陈酿,每隔一个月用移液管提取橡木桶中同一位置的干红葡萄酒,测定7项理化指标。结果表明:橡木桶陈酿过程中,p H值、总酸保持不变,色度、挥发酸和丹宁含量增加,而游离硫含量和色调明显下降。     

山核桃破壳机的设计

设计了一种基于挤压方式的山核桃破壳机械。特殊设计的螺旋碾桶和轧辊配合,实现山核桃破壳。选择轧楞倾角、碾桶螺距和轧辊转速为正交试验的3个因素,并通过极差分析和方差分析,确定轧楞倾角为15°、轧辊转速20 r/m in和碾桶螺距为2倍栅格宽度为其最优组合。试验结果表明,该设备破壳率99.4%、碎仁率为0.6%,改善了破壳质量,并提升了山核桃破壳机械化生产水平。     

人工催陈玫瑰酒香气变化的研究

[目的]研究玫瑰酒的人工催陈工艺。[方法]新发酵的玫瑰酒分别放玻璃瓶、橡木桶中常温陈酿,利用气相色谱-质谱仪（GC-MS）定期定量测定各香气成分的含量。[结果]玻璃瓶中,陈酿酒的苯乙醇含量先增后减,新酒和陈酿1、2个月后的苯乙醇含量分别为77.33%、85.93%和81.63%,其丁香酚含量变化不大,新酒和陈酿13、个月后的丁香酚含量分别为1.52%、1.44%和1.01%。橡木桶中,陈酿酒的苯乙醇含量逐渐上升,陈酿13、个月后的苯乙醇分别含量为84.56%和87.79%,其丁香酚含量明显上升,陈酿12、个月后的丁香酚含量分别为5.42%和7.93%。橡木桶陈酿的酒中产生的丁香酚、呋喃酮等香气成分结合玫瑰花的特征香气使玫瑰花酒的香气更加复合和具有趣味。[结论]加入橡木陈酿玫瑰花酒是较好的处理方法。     

Molecular characterization of the human beta 3-adrenergic receptor

Since the classification of beta-adrenergic receptors (beta-ARs) into beta 1 and beta 2 subtypes, additional beta-ARs have been implicated in the control of various metabolic processes by catecholamines. A human gene has been isolated that encodes a third beta-AR, here referred to as the "beta 3-adrenergic receptor." Exposure of eukaryotic cells transfected with this gene to adrenaline or noradrenaline promotes the accumulation of adenosine 3',5'-monophosphate; only 2 of 11 classical beta-AR blockers efficiently inhibited this effect, whereas two others behaved as beta 3-AR agonists. The potency order of beta-AR agonists for the beta 3-AR correlates with their rank order for stimulating various metabolic processes in tissues where atypical adrenergic sites are thought to exist. In particular, novel beta-AR agonists having high thermogenic, antiobesity, and antidiabetic activities in animal models are among the most potent stimulators of the beta 3-AR.     

Magnitude of the 2010 Gulf of Mexico oil leak

To fully understand the environmental and ecological impacts of the Deepwater Horizon disaster, an accurate estimate of the total oil released is required. We used optical plume velocimetry to estimate the velocity of fluids issuing from the damaged well both before and after the collapsed riser pipe was removed. We then calculated the volumetric flow rate under a range of assumptions. With a liquid oil fraction of 0.4, we estimated that the average flow rate from 22 April 2010 to 3 June 2010 was 5.6 × 10(4) ± 21% barrels/day (1.0 × 10(-1) meter(3)/second), excluding secondary leaks. After the riser was removed, the flow was 6.8 × 10(4) ± 19% barrels/day (1.2 × 10(-1) meters(3)/second). Taking into account the oil collected at the seafloor, this suggests that 4.4 × 10(6) ± 20% barrels of oil (7.0 × 10(5) meters(3)) was released into the ocean.     

Self-assembled aggregates of rod-coil block copolymers and their solubilization and encapsulation of fullerenes

Amphiphilic poly(phenylquinoline)-block-polystyrene rod-coil diblock copolymers were observed to self-organize into robust, micrometer-scale, spherical, vesicular, cylindrical, and lamellar aggregates from solution. These diverse aggregate morphologies were seen at each composition, but their size scale decreased with a decreasing fraction of the rigid-rod block. Compared to coil-coil block copolymer micelles, the present aggregates are larger by about two orders of magnitude and have aggregation numbers of over 10(8). The spherical and cylindrical aggregates have large hollow cavities. Only spherical aggregates with aggregation numbers in excess of 10(9) were formed in the presence of fullerenes (C60, C70) in solution, resulting in the solubilization and encapsulation of over 10(10) fullerene molecules per aggregate.     

酚类物质对葡萄酒品质的影响

酚类物质作为葡萄酒的"骨架"成分,在葡萄酒中起着十分重要的作用。在葡萄酒中,一般常见的酚类物质可概括为类黄酮和非类黄酮2类,这些酚类物质主要来源于葡萄的果实、果梗、酵母代谢以及储酒容器橡木桶等,它们直接影响着葡萄酒的色泽、口感和香气,对葡萄酒的品质和风味特征有很大的影响。     

Tertiary structure of plant RuBisCO: domains and their contacts

The three-dimensional structure of ribulose-1,5-biphosphate carboxylase-oxygenase (RuBisCO), has been determined at 2.6 A resolution. This enzyme initiates photosynthesis by combining carbon dioxide with ribulose bisphosphate to form two molecules of 3-phosphoglycerate. In plants, RuBisCO is built from eight large (L) and eight small (S) polypeptide chains, or subunits. Both S chains and the NH2-terminal domain (N) of L are antiparallel beta, "open-face-sandwich" domains with four-stranded beta sheets and flanking alpha helices. The main domain (B) of L is an alpha/beta barrel containing most of the catalytic residues. The active site is in a pocket at the opening of the barrel that is partly covered by the N domain of a neighboring L chain. The domain contacts of the molecule and its conserved residues are discussed in terms of this structure.     

云南省主栽甘蔗品种抗旱性鉴定

为确定云南省5个甘蔗主栽品种(粤糖93-159、新台糖10号、粤糖86-368、新台糖22号、云引3号)的抗旱性以及选择合适的抗旱性鉴定方法,在大棚桶栽条件下对5个处于伸长期的甘蔗品种进行干旱胁迫15 d。处理期间调查参试品种叶片衰老情况、株高伤害度、叶面积伤害度等形态指标及丙二醛含量、可溶性糖含量、脯氨酸含量、超氧化物歧化酶活性等生理指标。结果表明,综合各种生理指标的模糊隶属函数评价法比较客观,是一种较合适的抗旱性鉴定方法;结合形态指标和生理指标抗旱性鉴定来看,粤糖86-368为抗旱性最好的品种,其次为云引3号,适宜旱区种植。     

Localization of the pancreatic beta cell glucose transporter to specific plasma membrane domains

Immunocytochemical techniques revealed that the "liver-type" glucose transporter is present in the insulin-producing beta cells of rat pancreatic islets but not in other islet endocrine cells. Ultrastructural analysis of the transporter by the protein A-gold technique showed that it is restricted to certain domains of the plasma membrane, its density being sixfold higher in microvilli facing adjacent endocrine cells than in the flat regions of the plasma membrane. These results support a possible role for this glucose transporter in glucose sensing by beta cells and provide evidence that these cells are polarized.     

In vivo half-life of a protein is a function of its amino-terminal residue

When a chimeric gene encoding a ubiquitin-beta-galactosidase fusion protein is expressed in the yeast Saccharomyces cerevisiae, ubiquitin is cleaved off the nascent fusion protein, yielding a deubiquitinated beta-galactosidase (beta gal). With one exception, this cleavage takes place regardless of the nature of the amino acid residue of beta gal at the ubiquitin-beta gal junction, thereby making it possible to expose different residues at the amino-termini of the otherwise identical beta gal proteins. The beta gal proteins thus designed have strikingly different half-lives in vivo, from more than 20 hours to less than 3 minutes, depending on the nature of the amino acid at the amino-terminus of beta gal. The set of individual amino acids can thus be ordered with respect to the half-lives that they confer on beta gal when present at its amino-terminus (the "N-end rule"). The currently known amino-terminal residues in long-lived, noncompartmentalized intracellular proteins from both prokaryotes and eukaryotes belong exclusively to the stabilizing class as predicted by the N-end rule. The function of the previously described posttranslational addition of single amino acids to protein amino-termini may also be accounted for by the N-end rule. Thus the recognition of an amino-terminal residue in a protein may mediate both the metabolic stability of the protein and the potential for regulation of its stability.     

Evolution of a protein fold in vitro

A "switch" mutant of the Arc repressor homodimer was constructed by interchanging the sequence positions of a hydrophobic core residue, leucine 12, and an adjacent surface polar residue, asparagine 11, in each strand of an intersubunit beta sheet. The mutant protein adopts a fold in which each beta strand is replaced by a right-handed helix and side chains in this region undergo significant repacking. The observed structural changes allow the protein to maintain solvent exposure of polar side chains and optimal burial of hydrophobic side chains. These results suggest that new protein folds can evolve from existing folds without drastic or large-scale mutagenesis.     

Three-dimensional structure of poliovirus at 2.9 A resolution

The three-dimensional structure of poliovirus has been determined at 2.9 A resolution by x-ray crystallographic methods. Each of the three major capsid proteins (VP1, VP2, and VP3) contains a "core" consisting of an eight-stranded antiparallel beta barrel with two flanking helices. The arrangement of beta strands and helices is structurally similar and topologically identical to the folding pattern of the capsid proteins of several icosahedral plant viruses. In each of the major capsid proteins, the "connecting loops" and NH2- and COOH-terminal extensions are structurally dissimilar. The packing of the subunit "cores" to form the virion shell is reminiscent of the packing in the T = 3 plant viruses, but is significantly different in detail. Differences in the orientations of the subunits cause dissimilar contacts at protein-protein interfaces, and are also responsible for two major surface features of the poliovirion: prominent peaks at the fivefold and threefold axes of the particle. The positions and interactions of the NH2- and COOH-terminal strands of the capsid proteins have important implications for virion assembly. Several of the "connecting loops" and COOH-terminal strands form prominent radial projections which are the antigenic sites of the virion.     

阶段性养分亏缺对大豆茎部性状及产量的影响

以垦农4号大豆为试验材料,在桶栽砂培条件下,研究了9个不同生育阶段养分亏缺对大豆茎部性状及产量的影响。结果表明,大豆不同生育时期的阶段性养分亏缺,均可对大豆的茎部性状及产量产生一定影响。VE—V3期养分亏缺可显著降低株高及产量,是株型及产量调控的关键时期,其他各阶段的养分亏缺均可通过前期或后期的养分供应得到恢复。R5阶段充足的水分供应比养分对产量的影响更大,是水分需求的关键时期。