In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.

Q: Lipid rafts are micro-domains of ordered lipids (L o phase) in biological membranes. The L o phase of cellular membranes can be isolated from disordered lipids (L d phase) after treatment with 1 % Triton X-100 at 4°C in which the L o phase forms the detergent-resistant membrane (DRM) fraction. The lipid composition of DRM derived from Madin-Darby canine kidney (MDCK) cells, McArdle cells and porcine sperm is compared with that of the whole cell. Remarkably, the unsaturation and chain length degree of aliphatic chains attached to phospholipids is virtually the same between DRM and whole cells. Cholesterol and sphingomyelin were enriched in DRMs but to a cell-specific molar ratio. Sulfatides (sphingolipids from MDCK cells) were enriched in the DRM while a seminolipid (an alkylacylglycerolipid from sperm) was depleted from the DRM. Treatment with<5 mM methyl-ß-cyclodextrin (MBCD) caused cholesterol removal from the DRM without affecting the composition and amount of the phospholipid while higher levels disrupted the DRM. The substantial amount of (poly)unsaturated phospholipids in DRMs as well as a low stoichiometric amount of cholesterol suggest that lipid rafts in biological membranes are more fluid and dynamic than previously anticipated. Using negative staining, ultrastructural features of DRM were monitored and in all three cell types the DRMs appeared as multilamellar vesicular structures with a similar morphology. The detergent resistance is a result of protein-cholesterol and sphingolipid interactions allowing a relatively passive attraction of phospholipids to maintain the L o phase. For this special issue, the relevance of our findings is discussed in a sperm physiological context.

A: Ultrastructure and lipid composition of detergent-resistant membranes derived from mammalian sperm and two types of epithelial cells
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Q: Background: The HIV-1 RNA genome has a biased nucleotide composition with a surplus of As. Several hypotheses have been put forward to explain this striking phenomenon, but the A-count of the HIV-1 genome has thus far not been systematically manipulated. The reason for this reservation is the likelihood that known and unknown sequence motifs will be affected by such a massive mutational approach, thus resulting in replication-impaired virus mutants. We present the first attempt to increase and decrease the A-count in a relatively small polymerase (pol) gene segment of HIV-1 RNA. To minimize the mutational impact, a new mutational approach was developed that is inspired by natural sequence variation as present in HIV-1 isolates. This phylogeny-instructed mutagenesis allowed us to create replication-competent HIV-1 mutants with a significantly increased or decreased local A-count. The local A-count of the wild-type (wt) virus (40.2%) was further increased to 46.9% or reduced to 31.7 and 26.3%. These HIV-1 variants replicate efficiently in vitro, despite the fact that the pol changes cause a quite profound move in HIV-SIV sequence space. Extrapolating these results to the complete 9 kb RNA genome, we may cautiously suggest that the A-rich signature does not have to be maintained. This survey also provided clues that silent codon changes, in particular from G-to-A, determine the subtype-specific sequence signatures.

A: HIV-1 tolerates changes in A-count in a small segment of the pol gene
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Q: Severe acute respiratory syndrome (SARS) is a newly emerging infectious disease caused by a novel coronavirus (SARS-CoV), which has overwhelmed more than 30 countries claiming nearly 8400 cases with over 800 fatalities. Thanks to the unprecedented international collaboration, the whole-genomes of SARS-CoVs were successfully deciphered shortly after the identification of the causative pathogen for outbreak of SARS in southern China, in 2003. Hitherto, the SARS-CoV, as a viral paradigm of emerging infectious entities, has been extensively studied that has ranged from epidemiology, molecular virology/immunology to structural genomics. Also, several lines of breakthroughs have been record-brokenly obtained, that included the finding of ACE2, a functional receptor for the SARS-CoV, solution of the 3CL pro structure, a first crystal structure of SARS-related macromolecules, revealing of bats as natural reservoirs for SARS-like viruses and the possible involvement of civet cats in the SARS emergence. This review intends to outline the major progress in the journey of ARTICLE IN PRESS www.elsevier.com/locate/cimid 0147-9571/$ -see front matter r Re´sumeĹ e syndrome respiratoire aigu se´ve`re (SRAS ou SARS), une maladie infectieuse e´mergeante cause´e par un nouveau coronavirus (SARS-CoV), toucha plus de 8400 personnes causant 800 morts dans 30 pays diffe´rents. Graˆce a`la mise en place d'une collaboration internationale sans pre´ce´dent le de´cryptage du ge´nome complet du SARS-CoV fut re´alise´tre`s peu de temps apre`s l'identification de l'agent pathoge`ne suite au de´clenchement de l'e´pide´mie dans le sud de la Chine en 2003. Le SARS-CoV en temps que paradigme de maladies infectieuses e´mergeantes a fait l'objet d'une e´tude comple`te en passant de l'e´pide´miologie, la virologie/immunologie mole´culaire a`la ge´nomique structurale. Ainsi, c'est en un temps record qu'ont e´te´obtenues des donne´es majeures incluant la de´couverte de ACE2, un re´cepteur fonctionnel pour le SARS-CoV, la structure du 3CL pro premie`re structure cristallographique d'une macromole´cule du SARS, re´ve´lant que la chauve-souris e´tait le re´servoir naturel de virus du type SARS, et que la civette e´tait certainement a`l'origine de l'e´mergence du SRAS. Cette revue vise a`souligner les progre`s majeurs re´alise´s dans l'exploration du SRAS, en soulignant l'importance des travaux primordiaux et pre´coces re´alise´s par les chercheurs chinois. r

A:
Towards our understanding of SARS-CoV, an emerging and devastating but quickly conquered virus
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