Elena Perez | Universidad de Cadiz (original) (raw)

Papers by Elena Perez

Research paper thumbnail of Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California

Geochemistry Geophysics Geosystems, 2003

1] As part of an ongoing effort to explore the use of foraminifera as a means to assess modern an... more 1] As part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release, we compared ambient pore water chemistry with the distribution and stable isotopic composition of living (rose Bengal stained) foraminifera in MBARI ROV Ventana tube cores taken from modern seepage areas (about 1000 m water depth) in Monterey Bay, California. Benthic foraminiferal isotopic differences between sites clearly indicate that methane-influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry. Carbon isotope signatures of living benthic foraminifera did not conform to the very negative (À30 to À48%), methane-influenced carbon isotope values of the pore waters they live in. Instead, the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published d 13 C values of foraminifera living in nonseep habitats. It is not clear what relative influences biological, ecological, and physical factors have on the carbon isotopic signatures observed in seep foraminifera. Substantial carbon isotope differences can exist between individuals of the same seep species. For instance, d 13 C values of living Globobulimina pacifica varied by as much as 2.9% between seeps within 8 km of each other, whereas d 13 C values of living Uvigerina peregrina varied by as much as 1.95% within the same seep. Provided there is no diagenetic alteration of the test carbonate, isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage.

Research paper thumbnail of IMPINGEMENT DRYING OF POTATO CHIPS

Journal of Food Process Engineering, 2002

The effect of superheated steam temperature (115, 130, and 145C) and convective heat transfer coe... more The effect of superheated steam temperature (115, 130, and 145C) and convective heat transfer coefficient (100 and 160 W/m2C) on the drying rate and product quality attributes (shrinkage, density, porosity, color, texture, and nutrition loss) of potato chips was investigated. Furthermore, potato chips dried by impinging superheated steam (130 and 145C, h = 100 W/m2C) were compared to air dried (same conditions), commercial, and fried potato chips.Temperature and convective heat transfer coefficient had a significant effect on the drying rate during superheated steam impingement drying. Potato chips dried at higher drying temperature and convective heat transfer coefficient showed less shrinkage, lower bulk density, higher porosity, and darker color when compared to chips dried at lower temperatures and convective heat transfer coefficients. They were also less hard and had a lower vitamin C content.A higher rate of evaporation during the falling rate period was obtained when superheated steam drying was compared to air impingement drying. Potato chips produced using superheated steam impingement drying showed more shrinkage, higher bulk density, lower porosity, and lighter color than chips dried with air under the same temperature and with the same convective heat transfer coefficient (130, and 145C, h = 100 W/m2C). Moreover, superheated steam-dried potato chips retained more vitamin C during the drying process.

Research paper thumbnail of Natural Variation in HIV1 Protease, Gag p7 and p6, and Protease Cleavage Sites within Gag/Pol Polyproteins: Amino Acid Substitutions in the Absence of Protease Inhibitors in Mothers and Children Infected by Human Immunodeficiency Virus Type 1

Virology, 1996

Reduced sensitivity of human immunodeficiency virus type 1 (HIV-1) to protease inhibitors is asso... more Reduced sensitivity of human immunodeficiency virus type 1 (HIV-1) to protease inhibitors is associated with multiple amino acid substitutions in the virus-encoded protease. The combination of changes that contribute to drug resistance is dependent in part upon the amino acid residues comprising protease alleles prior to drug therapy. We analyzed within peripheral blood mononuclear cells from HIV-1-infected mothers and their children viral gag/pol regions, which included p7, transframe p6/p6*, and protease coding sequences, as well as six protease cleavage sites. Sixty protease alleles from 12 individuals differed by at least 3 to as many as 10 amino acids from proteases encoded by molecular clones of HIV-1, indicating that there is no prototype or consensus wild-type HIV-1 protease sequence. Protease variants with a proline at position 63, a substitution associated with resistance to protease inhibitors, appeared in the absence of antiprotease therapy in 7 patients and were transmitted by 2 mothers to their infants. Gag p7 and p6 regions were significantly more variable than protease. The p6/p6* region contained length variants and amino acid repeats in both reading frames. Five protease cleavage sites (B, D, D, E, and F) contained highly conserved amino acid sequences in individuals infected by epidemiologically distinct viruses. In contrast, C cleavage sites, localized between Gag p2 and Gag p7, displayed considerable amino acid variability, were unique among groups of infected individuals, and appeared to be related to particular protease alleles. Genetic variability in vivo in protease, in cleavage sites, and in proteins upstream of protease provides the potential to modulate enzyme activity and susceptibility to protease inhibitors. ᭧

Research paper thumbnail of Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California

Geochemistry Geophysics Geosystems, 2003

1] As part of an ongoing effort to explore the use of foraminifera as a means to assess modern an... more 1] As part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release, we compared ambient pore water chemistry with the distribution and stable isotopic composition of living (rose Bengal stained) foraminifera in MBARI ROV Ventana tube cores taken from modern seepage areas (about 1000 m water depth) in Monterey Bay, California. Benthic foraminiferal isotopic differences between sites clearly indicate that methane-influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry. Carbon isotope signatures of living benthic foraminifera did not conform to the very negative (À30 to À48%), methane-influenced carbon isotope values of the pore waters they live in. Instead, the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published d 13 C values of foraminifera living in nonseep habitats. It is not clear what relative influences biological, ecological, and physical factors have on the carbon isotopic signatures observed in seep foraminifera. Substantial carbon isotope differences can exist between individuals of the same seep species. For instance, d 13 C values of living Globobulimina pacifica varied by as much as 2.9% between seeps within 8 km of each other, whereas d 13 C values of living Uvigerina peregrina varied by as much as 1.95% within the same seep. Provided there is no diagenetic alteration of the test carbonate, isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage.

Research paper thumbnail of IMPINGEMENT DRYING OF POTATO CHIPS

Journal of Food Process Engineering, 2002

The effect of superheated steam temperature (115, 130, and 145C) and convective heat transfer coe... more The effect of superheated steam temperature (115, 130, and 145C) and convective heat transfer coefficient (100 and 160 W/m2C) on the drying rate and product quality attributes (shrinkage, density, porosity, color, texture, and nutrition loss) of potato chips was investigated. Furthermore, potato chips dried by impinging superheated steam (130 and 145C, h = 100 W/m2C) were compared to air dried (same conditions), commercial, and fried potato chips.Temperature and convective heat transfer coefficient had a significant effect on the drying rate during superheated steam impingement drying. Potato chips dried at higher drying temperature and convective heat transfer coefficient showed less shrinkage, lower bulk density, higher porosity, and darker color when compared to chips dried at lower temperatures and convective heat transfer coefficients. They were also less hard and had a lower vitamin C content.A higher rate of evaporation during the falling rate period was obtained when superheated steam drying was compared to air impingement drying. Potato chips produced using superheated steam impingement drying showed more shrinkage, higher bulk density, lower porosity, and lighter color than chips dried with air under the same temperature and with the same convective heat transfer coefficient (130, and 145C, h = 100 W/m2C). Moreover, superheated steam-dried potato chips retained more vitamin C during the drying process.

Research paper thumbnail of Natural Variation in HIV1 Protease, Gag p7 and p6, and Protease Cleavage Sites within Gag/Pol Polyproteins: Amino Acid Substitutions in the Absence of Protease Inhibitors in Mothers and Children Infected by Human Immunodeficiency Virus Type 1

Virology, 1996

Reduced sensitivity of human immunodeficiency virus type 1 (HIV-1) to protease inhibitors is asso... more Reduced sensitivity of human immunodeficiency virus type 1 (HIV-1) to protease inhibitors is associated with multiple amino acid substitutions in the virus-encoded protease. The combination of changes that contribute to drug resistance is dependent in part upon the amino acid residues comprising protease alleles prior to drug therapy. We analyzed within peripheral blood mononuclear cells from HIV-1-infected mothers and their children viral gag/pol regions, which included p7, transframe p6/p6*, and protease coding sequences, as well as six protease cleavage sites. Sixty protease alleles from 12 individuals differed by at least 3 to as many as 10 amino acids from proteases encoded by molecular clones of HIV-1, indicating that there is no prototype or consensus wild-type HIV-1 protease sequence. Protease variants with a proline at position 63, a substitution associated with resistance to protease inhibitors, appeared in the absence of antiprotease therapy in 7 patients and were transmitted by 2 mothers to their infants. Gag p7 and p6 regions were significantly more variable than protease. The p6/p6* region contained length variants and amino acid repeats in both reading frames. Five protease cleavage sites (B, D, D, E, and F) contained highly conserved amino acid sequences in individuals infected by epidemiologically distinct viruses. In contrast, C cleavage sites, localized between Gag p2 and Gag p7, displayed considerable amino acid variability, were unique among groups of infected individuals, and appeared to be related to particular protease alleles. Genetic variability in vivo in protease, in cleavage sites, and in proteins upstream of protease provides the potential to modulate enzyme activity and susceptibility to protease inhibitors. ᭧