Frequency shifting of pulsed narrow-band laser light in a multipass Raman cell

A multipass cell is described which allows efficient stimulated Raman frequency shifting for low pump laser intensities and low gas pressures. The latter is important for Raman shifting of narrow-band Fourier-transform limited light pulses (Δv=75 MHz). It is shown that frequency broadening of the Raman shifted light can be largely avoided in the Dicke narrowing regime at low pressures. For 75 MHz pump pulses and an H2 density of 2.5 amagat we found a negligible broadening to 90 MHz of the stimulated Stokes light. This is far below the value of 250 MHz expected from spontaneous emission. The narrow-band Stokes pulses achieved in CO2 enabled us to measure the pressure shift coefficient (-0.71×10-2 cm-1/amagat) of this gas. It is demonstrated, for the example of benzene, that our technique provides a very practical light source for high resolution molecular spectroscopy

Epistasis Among Adaptive Mutations in Deer Mouse Hemoglobin

Epistatic interactions between mutant sites in the same protein can exert a strong influence on pathways of molecular evolution. We performed protein engineering experiments that revealed pervasive epistasis among segregating amino acid variants that contribute to adaptive functional variation in deer mouse hemoglobin (Hb). Amino acid mutations increased or decreased Hb-O2 affinity depending on the allelic state of other sites. Structural analysis revealed that epistasis for Hb-O2 affinity and allosteric regulatory control is attributable to indirect interactions between structurally remote sites. The prevalence of sign epistasis for fitness-related biochemical phenotypes has important implications for the evolutionary dynamics of protein polymorphism in natural populations

The mechanistic basis of hemoglobin adaptation in the high-flying barheaded goose: insights from ancestral protein resurrection

The bar-headed goose (‘BHG’, Anser indicus) is renowned for its trans-Himalayan migratory flights, and the elevated hemoglobin (Hb)-O2 affinity of this species is thought to make a key contribution to its capacity for powered flight at elevations of ~9000 m. Here we revisit the molecular basis of this text-book example of biochemical adaptation. Previous hypotheses about the molecular basis of the evolved increase in Hb-O2 affinity were tested by engineering BHGspecific mutations into recombinant human Hb. This approach can provide important insights, but one problem with such ‘horizontal’ comparisons – swapping residues between proteins of contemporary species – is that the focal mutations are introduced into a sequence context that may not be evolutionarily relevant. If mutations have context-dependent effects, then introducing BHG-specific substitutions into human Hb may not recapitulate the functional effects of causative mutations on the genetic background in which they actually occurred during evolution (i.e., in the BHG ancestor). An alternative ‘vertical’ approach is to reconstruct and resurrect ancestral proteins to test the effects of historical mutations on the genetic background in which they actually occurred. We used this approach to measure the independent and joint effects of amino acid substitutions that occurred in the reconstructed BHG ancestor. Measuring the additive and nonadditive effects of these substitutions enabled us to address several important evolutionary questions about molecular adaptation: (1) Do each of the substitutions contribute to the increased Hb-O2 affinity? If so, what are their relative effects? (2) Does the sequential order in which they occur make a difference? In other words, do the functional effects of mutations depend on which other substitutions have already occurred

The mechanistic basis of hemoglobin adaptation in the high-flying barheaded goose: insights from ancestral protein resurrection

The bar-headed goose (‘BHG’, Anser indicus) is renowned for its trans-Himalayan migratory flights, and the elevated hemoglobin (Hb)-O2 affinity of this species is thought to make a key contribution to its capacity for powered flight at elevations of ~9000 m. Here we revisit the molecular basis of this text-book example of biochemical adaptation. Previous hypotheses about the molecular basis of the evolved increase in Hb-O2 affinity were tested by engineering BHGspecific mutations into recombinant human Hb. This approach can provide important insights, but one problem with such ‘horizontal’ comparisons – swapping residues between proteins of contemporary species – is that the focal mutations are introduced into a sequence context that may not be evolutionarily relevant. If mutations have context-dependent effects, then introducing BHG-specific substitutions into human Hb may not recapitulate the functional effects of causative mutations on the genetic background in which they actually occurred during evolution (i.e., in the BHG ancestor). An alternative ‘vertical’ approach is to reconstruct and resurrect ancestral proteins to test the effects of historical mutations on the genetic background in which they actually occurred. We used this approach to measure the independent and joint effects of amino acid substitutions that occurred in the reconstructed BHG ancestor. Measuring the additive and nonadditive effects of these substitutions enabled us to address several important evolutionary questions about molecular adaptation: (1) Do each of the substitutions contribute to the increased Hb-O2 affinity? If so, what are their relative effects? (2) Does the sequential order in which they occur make a difference? In other words, do the functional effects of mutations depend on which other substitutions have already occurred

Predictable convergence in hemoglobin function has unpredictable molecular underpinnings

To investigate the predictability of genetic adaptation, we examined the molecular basis of convergence in hemoglobin function in comparisons involving 56 avian taxa that have contrasting altitudinal range limits. Convergent increases in hemoglobin-oxygen affinity were pervasive among high-altitude taxa, but few such changes were attributable to parallel amino acid substitutions at key residues.Thus, predictable changes in biochemical phenotype do not have a predictable molecular basis. Experiments involving resurrected ancestral proteins revealed that historical substitutions have context-dependent effects, indicating that possible adaptive solutions are contingent on prior history. Mutations that produce an adaptive change in one species may represent precluded possibilities in other species because of differences in genetic background

Predictable convergence in hemoglobin function has unpredictable molecular underpinnings

To investigate the predictability of genetic adaptation, we examined the molecular basis of convergence in hemoglobin function in comparisons involving 56 avian taxa that have contrasting altitudinal range limits. Convergent increases in hemoglobin-oxygen affinity were pervasive among high-altitude taxa, but few such changes were attributable to parallel amino acid substitutions at key residues.Thus, predictable changes in biochemical phenotype do not have a predictable molecular basis. Experiments involving resurrected ancestral proteins revealed that historical substitutions have context-dependent effects, indicating that possible adaptive solutions are contingent on prior history. Mutations that produce an adaptive change in one species may represent precluded possibilities in other species because of differences in genetic background

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix. Corrigendum

In the article by Inoguchi et al. (2013) the affiliation for two of the authors, Angela Fago and Roy E. Weber, was given incorrectly. The correct affiliation is Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark

The Ursinus Weekly, October 25, 1948

Ranung and Klein to offer musicale; program to feature folk songs, arias • Fowler, two profs give party views in opening forum • Campus election slated for Wednesday; enthusiasm runs high among students • \u27Y\u27 committees plan numerous activities • Sororities to begin sophomore rushing • Week-end cheerful despite grid loss • Luncheons attended by many ex-coeds • Curtain Club plans show for November presentation • Officers of IRC to attend conference at Penn State • Frosh bear fund reaches $28 in drive to buy new costume • Frosh hold annual banquet with Gene Glick as guest • Chem society begins year; executive committee voted • Ruby will conduct raffle in new subscription drive • Bachelors number 338 as total vets enrollment reaches 423 • Freshman relates experiences abroad • How to make your room inhabitable • Introducing Steve Arvanitis • Gridders to tackle Staten Island team • JVs held scoreless in Hill soccer tilt • Sam Gary tosses four touchdown aerials as Swarthmore wins old timers\u27 battle 24-7 • Seeders calls team for hoop practice • Co-ed JVs extend undefeated record • Lafayette tramples varsity booters 9-0 • Soccer squad clips alumni booters 4-0 • Varsity tripped 2-0 by hockey alumnae • Hayseed fans shine at junior shindig • WSGA names three women to nominating committee • Cub & Key holds first meeting; dinner in Philadelphia plannedhttps://digitalcommons.ursinus.edu/weekly/1599/thumbnail.jp

Deer mouse hemoglobin exhibits a lowered oxygen affinity owing to mobility of the E helix

The deer mouse, Peromyscus maniculatus, exhibits altitude-associated variation in hemoglobin oxygen affinity. To examine the structural basis of this functional variation, the structure of the hemoglobin was solved. Recombinant hemoglobin was expressed in Escherichia coli and was purified by ion-exchange chromatography. Recombinant hemoglobin was crystallized by the hangingdrop vapor-diffusion method using polyethylene glycol as a precipitant. The obtained orthorhombic crystal contained two subunits in the asymmetric unit. The refined structure was interpreted as the aquo-met form. Structural comparisons were performed among hemoglobins from deer mouse, house mouse and human. In contrast to human hemoglobin, deer mouse hemoglobin lacks the hydrogen bond between α1Trp14 in the A helix and α1Thr67 in the E helix owing to the Thr67Ala substitution. In addition, deer mouse hemoglobin has a unique hydrogen bond at the α1β1 interface between residues α1Cys34 and β1Ser128

Genetically based low oxygen affinities of felid hemoglobins: Lack of biochemical adaptation to high-altitude hypoxia in the snow leopard

Genetically based modifications of hemoglobin (Hb) function that increase blood–O2 affinity are hallmarks of hypoxia adaptation in vertebrates. Among mammals, felid Hbs are unusual in that they have low intrinsic O2 affinities and reduced sensitivities to the allosteric cofactor 2,3-diphosphoglycerate (DPG). This combination of features compromises the acclimatization capacity of blood–O2 affinity and has led to the hypothesis that felids have a restricted physiological niche breadth relative to other mammals. In seeming defiance of this conjecture, the snow leopard (Panthera uncia) has an extraordinarily broad elevational distribution and occurs at elevations above 6000 m in the Himalayas. Here, we characterized structural and functional variation of big cat Hbs and investigated molecular mechanisms of Hb adaptation and allosteric regulation thatmay contribute to the extreme hypoxia tolerance of the snow leopard. Experiments revealed that purified Hbs from snow leopard and African lion exhibited equally low O2 affinities and DPG sensitivities. Both properties are primarily attributable to a single amino acid substitution, β2His→Phe, which occurred in the common ancestor of Felidae. Given the low O2 affinity and reduced regulatory capacity of feline Hbs, the extreme hypoxia tolerance of snow leopards must be attributable to compensatory modifications of other steps in the O2-transport pathway