Review: Reef Fishes in Biodiversity Hotspots Are at Greatest Risk from Loss of Coral Species

In the article, “Reef Fishes in Biodiversity Hotspots Are at Greatest Risk from Loss of Coral Species”, Holbrook and other researchers bring to the readers attention the importance of coral reef systems that are currently under attack from numerous global and anthropogenic changes. The researchers hypothesize that the effect of damaging habitats will be the strongest where there is the highest biodiversity because of the specialization by the fishes there. Although there were experiments done on similar hypothesis, the author pointed out that their specific hypothesis has not been tested yet. Therefore, the study’s main research question is “How will different geographically diverse communities respond to identical changes to the diversity of the corals in the region?”

In the article, the researchers conducted the main study with building 45 different patch reefs with different levels of coral diversity on large flat sandy areas with no other habitat in the same area in three locations with different levels of biodiversity. Over a course of 8-12 months, divers recorded the different species that were on or interacted with the patch reefs four times. After the collection, the data were analyzed by using the total number of species on each patch during the final survey. The researchers used canonical analysis of principal coordinates (CAP) to find the influence of the coral species on the fish communities. The sample size was different in the three locations so Type III Sums of Squares was also used to find statistical significance.

The researchers found that the relationship between biodiversity and habitat providing corals correlates positively with the size of the regional species pool. They argue that species that are specific to their habitat in areas with high biodiversity are at a higher risk of local extinction compared to the regions with lower species richness because those areas are faced with many global environmental changes. The researchers also bring up two points that may contribute to the higher risk of local extinction. One, fish that that have high specialization often also often exist in small population sizes, which escalates local extinction. Second, co-occurring coral species differ in the biodiversity of the species they support. Therefore, if these corals that have a high habitat providing functions are depleting, the species there will also have a local extinction risk. Lastly, the author also argues that if communities with high diversity are vulnerable to a greater extinction risk, then this implies that regions of lower biodiversity will be more resistant to the reductions in coral species.

The information in the article is consistent with previous knowledge about coral reefs ecosystems and the different threats they face. Overall, the researchers make valid conclusions from the analysis of the data, however, some inferences cannot be completely justified. The communities with lower diversity will be more resistant to reductions in the diversity of the coral habitats is a weak argument because ‘resistance’ implies that they are actively against the reductions whereas the data only shows that there is a higher chance of local extinction in species-rich areas. Information from this article would be most beneficial to other scientists that focus on future implications of the global and anthropogenic changes on the extinction rates of various species.

Coral reefs currently house one-third of the marine species in the world and often exist in areas with high biodiversity. Research has found that areas with high biodiversity are at a higher risk for local extinction of species because of the specialization of the species there. With this new information, we can better understand the repercussions of the changes we impose on the environment and work to correct those for future generations.

Literature Cited

Holbrook SJ, Schmitt RJ, Messmer V, Brooks AJ, Srinivasan M, Munday PL, et al. (2015) Reef Fishes in Biodiversity Hotspots Are at Greatest Risk from Loss of Coral Species. PLoS ONE 10(5): e0124054. doi:10.1371/journal.pone.0124054

Get the Kids to Bed: A Longitudinal Study Correlates Sleep to Wellness in Adolescents

A recent study conducted among adolescents in Norway and Switzerland made an important connection between the duration of sleep received, and one’s psychological well-being. Researchers at the University of Basel wanted to find out if decreased sleep duration in adolescents is a good predictor of lower subjective psychological across the span of one year. The article draws from the knowledge base of sleep studies associating longer sleep with a greater sense of well-being. It adds to that knowledge by studying the effects of reduced sleep over a long term with a large sample size.

Eight hundred eighty-six adolescents from Switzerland and seven hundred fifteen adolescents in Norway were asked to report the time they had gone to bed and time they had woken up on a day in May of 2012, 6 months later in November, and again the following May. This was done during a public school lesson and followed with a series of surveys given to assess subjective psychological well-being (SPW).

The researchers analyzed the by splitting them into groups and correlating each group’s sleep duration scores with their SPW scores. There were three age groups per country: 10-11 year olds, 12-13 year olds and 14-15 year olds. The sleep durations of the six total groups were correlated with subjective psychological well being scores at the three times data were measured (May 2012, November 2012 and March 2013). There were a total of 18 resulting correlations, one correlation for each of the three age groups, in each country, at each data collection wave.

The authors argue that adolescents who get more sleep have a higher sense of well-being. Although sixteen of the eighteen groups exhibited a statistically significant positive relationship between sleep duration and well-being, the size of the correlation was quite small. This suggests that although sleep is definitely important, it’s not a paramount predictor of well being. Additionally, pre-bed-time behaviors which influence sleep quality have been shown to be an important predictor of well being, yet the authors neglected test for this variable. Also, instead of attempting to derive causality by using SPW at a given time as a predictor of sleep, the study should implement an experimental design which increases sleep and measures SPW for further research. This would likely have to be done with a smaller sample size but would serve as an excellent supplement if similar age groups and sampling regions are used.

Although the study had its shortcomings, this is often the case among scientific research and the findings of this study have important implications. Is sleep undervalued in modern society? If we know that sleeping more causes adolescents to feel better about themselves, should we provide more education in public schools on the benefits of increased sleep? Moving forward it’s probably best to keep these benefits in mind and use them to guide decisions in parenting and education. May the next generation of adolescents rest well so we develop a population of healthy, mentally strong young adults.

The Search for Extragalactic Aliens in 2015

Are we alone in our universe or not? Answering this question seems to be purely science fiction. Yet, for several decades, since the birth of the radio humanity has been probing the sky for messages from ET’s (Extraterrestrial’s). We have also been sending our own messages out into space. In hopes that we may spur contact with an alien species. Scientists have been studying the probability of ET existence since the 1900’s. In a universe of over 100 billion galaxies each with 100 billion stars there simply must exist other life forms. If not than the probability of us existing would literally be zero. Earth would actually be one out of 1000 quintillion. From a non-humancentric point of view, that statistic is impossible to swallow. Many studies have been done to attempt to find or communicate with these aliens. The Drake Equation gave a qualitative and quantitative analysis of the probability of there being other aliens. The Kardashev paper classifies different types of aliens. The Dyson paper reports on possible astroengineering projects advanced aliens might conduct. Then there is the Fermi Paradox, which questions why in a universe that is suppose to be thriving of life and intelligence, have we not yet found ET’s. This question epitomizes the endless search many have done, to only turn up nothing. A study published this year by (Zackrisson et al) attempted to advance the search for alien life forms even more. This time the team of scientists wanted to know, instead of trying to directly communicate with aliens, could we probe for galactic class aliens by searching for the effects of their existence in the night sky, in their galaxies.

Earlier searches for aliens sent out messages and attempted to find other messages from other civilizations. However, this would mean that an alien species would have to know of our existence. Because a message that can be read must be aimed directly at Earth. If they wanted to send a signal out in all directions an immense amount of energy would be needed. This is how Kardashev, a Soviet scientist began to classify three types of civilizations. The questions started by attempting to solve how much energy would be needed to send a signal in all directions. Then turned into classifying energy levels of advanced civilizations. Kardashev determined that there are 3 civilization types. They are planetary, solar, and galactic, a species becomes solar, for example when it has used all the energy from its sun, and galactic when all the energy from its galaxy. This classification leaves little to dispute with. This is because Kardashev offers no means of getting these energies, only that this energy would be necessary to support these civilizations, and their massive projects. And it indeed would be necessary. Also it follows the growth of humans energy needs up till now, and quantifies that in terms of suns, as the sun outputs an very high amount of energy. It is a possibility that these aliens would get the energy needed from the sun. This is when Dyson proposed the Dyson sphere. Keep in mind a true Dyson sphere is not a hollow ball that surrounds a star like in sci-fi movies, rather a cloud of solar panel satellites that orbit their star. This lead to a change in direction in how scientists were searching for aliens. However, scientists later determined that it is better to search for aliens in a more indirect way, such as finding traces of their existence. In creating a Dyson sphere or cloud, the solar panels would absorb much of the energy from the sun. However, via the 1st law of thermodynamics thermal radiation would be re radiated by these panels. This would give a star this weird light curve, and scientists know the common light curves of a star, and if the light curve does not look like the normal, there may be a Dyson sphere there. This was the premise for a 1999 study by Annis that attempted to find these changes on a galactic scale. However, though the study turned up a conclusion that such dimmed galaxies did not exist, they only used 50 galaxies. That is where this more current study picks up.

Published in the September version of The Astrophysical Journal is a paper that attempts to advance the search for ET’s. This time the researchers will be using a massive database of galaxies from which they will study 1400 galaxies. There is also a known relationship in astrophysics known as the Tully Fisher relationship. Essentially, for certain galaxy types (such as spiral) there is a clear relationship between the brightness and the rotation speed and the mass of a galaxy. This dataset is much larger than the previous study done in 1999. But the researchers also made sure to minimize the uncertainty wherever they could. They used only galaxy clusters that could very easily have the cluster’s distance measured. This is important because the farther out a galaxy is the greater its redshift will be. Scientists use this redshift to measure the true brightness of galaxies (making them all comparable despite different distances and dimming). Thus having an accurate reading of the clusters brightness means a more accurate reading on any galaxy within that cluster that may have galactic aliens taking over, and thus be dimmer. These candidates would appear to be outliers relative to the rest of their galaxy cluster. The researchers had to carefully select their galaxies. For instance a set of galaxies within a cluster were weirdly dimmed. It was a possible “Eureka” moment. But the scientists determined that they were instead another cluster much farther away and that they needed to ignore those galaxies in their results. In the end the researchers determined that around .3% or slightly less of the galaxies surveyed could be Kardashev type 3 (galactic aliens) candidates. For many of these candidates natural phenomena both known or unknown was attributed to the findings. The paper determined that current methods might not be enough. One of the possible additions to the study could be to look for semi-galactic civilizations, where instead of an entire galaxy being dimmed and trying to search for that, only a portion of the disk of a galaxy would be oddly darkened. This would still be difficult to study because of all of the dark clouds that exist in our galaxy and others that might create false data.

These indirect astrophysical studies of aliens create a few theoretical qualms. For instance the Kardashev Type civilizations are based off of energy necessity, which is difficult to dispute. However, the proposed solution to attaining such energy, a Dyson sphere is not theoretically sound. Of course there a myriad of other unforeseeable technologies that could be invented on Earth in the next hundred years that could make solar power technology obsolete. Stating that solar technology is a must is a very difficult statement to make. However, considering probability, it could indeed be possible that at least one advanced civilization is using solar power. Then there is the other problem about assuming that civilizations need to reach a galactic scale or ever will. Current theoretical restrictions on the speed of light and a lack of a way around that restriction make galactic travel seem impossible. But again unforeseeable technology could arise and make that previous statement false. Then there is also this. In 1999 Annis (a different paper) published an article that suggested that a phase shift was currently occurring in our galaxy. That GRB, or massive concentrated bursts of energy from various astronomical phenomena could easily cause extinctions around the galaxy and on Earth. The paper also found that the mean time between GRB occurrence and the mean time for intelligent life evolution have for a long period of time been at odds with one another. An intelligent species would be on the verge of evolving and then “flash” and all of a sudden they are extinct. Only recently (meaning the past hundreds of thousands of years) has the period of GRB flashes and intelligent evolution become the same. Meaning that soon a phase shift will be occurring, where intelligent life thrives all around the galaxy as GRB’s become less frequent. This is good news for our galaxy but poses a question for researchers attempting to search for ET’s in other galaxies. If we consider that for spiral galaxy (same galaxy type as us) that this phase transition time is the same per galaxy, and that we are looking at galaxies in their past due to restrictions forced by the speed of light then it’s entirely possible that these galaxies too are undergoing a phase transition currently, but that we are looking at them at a much younger age, before this transition occurs. It would mean that we would not be able to see these aliens, even if these galaxies have the right properties to allow for their existence. This would limit our capacity to ever look for such aliens until these galaxies, from our perspective of us in the past become old enough for us to see intelligent life thrive there as well. This phase transition too poses another question, why are we one of the few planets to be spared by a GRB during our evolution. Some theories state that the late Ordovician Extinction occurred via a GRB event, but the paper states that every day civilizations in our galaxy are being killed by GRB’s, yet we have not been. This points to a statement that Earth is statistically lucky in not having its species killed off. Or perhaps there are other reasons and even more phase transitions like this related to life thriving in the habitat of the universe.

Though this paper provided a conclusion that did not find aliens, and though there are some fundamental theoretical questions that remained unsolved, this paper pioneers a way to search for aliens. This method of searching for aliens in galaxies far away by their effects on a galaxy is definitely going in the right direction. These studies need more work, but these researchers are determined to end the Fermi Paradox. And to finally answer that great question, are we alone?

Main Citation

Zackrisson, E; Calissendorff, P; Asadi, S; Nyholm, A. 2015 Extragalactic Seti: The Tully-Fisher Relation as a probe for Dysonian Astro Engineering in disk galaxies, The Astrophysical Journal, 39, 511-548

Other Citations

Annis, J. 1999, An Astrophysical Explanation for the Great Silence, Experimental Astrophysics Group

Annis, J. 1999, Placing A Limit on Star-Fed Kardashev Type III Civilisations, JBIS, 52, 33

Dyson, F. 1960, Search for artificial stellar sources, Science, 131, 1667

Kardashev, N. S. 1964,Transmission of information by extraterrestrial civilizations, Soviet Astronomy, 8, 217

Emotion Dysregulation May Not Be Solely Attributed to ADHD

The article “Emotion Regulation in Adolescent Males with Attention-Deficit Hyperactivity Disorder: Testing the Effects of Comorbid Conduct Disorder” was written by Northover, C., Thapar, A., Langley, K., and Goozen, S. The researchers’ essentially state that although attention-deficit hyperactivity disorder (ADHD) has often been associated with emotion dysregulation, it is not a unique characteristic of ADHD. Since few studies have actually experimentally investigated this while considering the effects of comorbid conduct disorder (CD), emotion dysregulation may not actually be a core trait of ADHD. CD is a psychological disorder within children or adolescents that is characterized by a range of problematic behaviors, including defiant behaviors and antisocial activities. Overall, this article does well in informing the reader while trying to reform the original view of ADHD.

This present study has taken the initiative in comparing adolescent boys with ADHD, ADHD + CD, and typical controls by using an economic decision-making game known as the Ultimatum Game (UG). The UG is a way of measuring emotion regulation by analyzing its effects on decision-making. This involved two players with an opportunity to split a total of 10 points, one being the proposer and the other being the responder. The offers varied in fairness, allowing the contribution of ADHD and CD symptom scores to the acceptance levels of unfair offers, to be analyzed. A total of 231 participants were recruited and categorized into four groups. These groups included ADHD, ADHD with low aggressive CD symptoms, ADHD with high aggressive CD symptoms, and a control. There was no significant difference in acceptance rates between groups for the fair offers and the highly unfair offers. However, the groups differed significantly for the moderately unfair offers. The group with ADHD and high aggressive CD symptoms were found to have rejected significantly more moderately unfair offers. Ultimately the results and the analysis suggest that it’s the subgroup of boys with ADHD and high aggressive CD that has trouble regulating emotion, which results in more “irrational” decisions. Another important outcome was that the group with only ADHD didn’t differ from the control group in performance on the task.

This article was quite clear and thorough in explaining the idea behind the common association of emotion dysregulation to ADHD, as well as the arguments for and against it.

Several issues within this study can be found however. The study only focused on male adolescents rather than both male and female; therefore the results may not necessarily be extended to all children with ADHD.

The study also didn’t normalize the number of samples per group. The four groups consisted of 47, 90, 64, and 30 participants. Although in certain experiments the samples per group isn’t always standardized, the lower number of 30 participants within the ADHD with high aggressive CD symptoms group that produced the statistically different results might have affected the significance.

Despite these issues, there is a sufficient amount of evidence in support of the idea that emotion dysregulation is not attributed to ADHD alone. Those who are interested in learning more about ADHD, UG, and how emotion dysregulation affects adolescents are encouraged to read the full article.

As a result of this recent article, we can better understand that those who are diagnosed with ADHD don’t necessarily have an underlying problem with regulating emotion too. Those with only ADHD provided the same results as those in the control group, showing that their decision-making in the UG sense is very similar to the rest of us. With these findings and results, the article contributes important information that calls for further investigation within this field.

Literature Cited

Northover, C., Thapar, A., Langley, K., & Goozen, S. (2015). Emotion Regulation in Adolescent Males with Attention-Deficit       Hyperactivity Disorder: Testing the Effects of Comorbid Conduct Disorder. Brain Sciences, 5(3), 369-386.

Review: Invasive species and their parasites: eastern cottontail rabbit Sylvilagus floridanus and Trichostrongylus affinis (Graybill, 1924) from Northwestern Italy

Researchers Tizzani, Catalano, Rossi, Duignan, and Meneguz published an article entitled, “Invasive species and their parasites: eastern cottontail rabbit Sylvilagus floridanus and Trichostrongylus affinis (Graybill, 1924) from Northwestern Italy” in the Parasitology Research journal in 2014. The article discusses the possibility of other parasite species being present in the invasive eastern cottontail Sylvilagus floridanus in Europe other than the species that have already been reported. This article presents the first documentation of the nematode Trichostrongylus affinis in a S. floridanus in Europe but provides no concrete evidence that explains the nematode’s presence in the invasive cottontails of Europe.

The researchers seek to find out whether or not there are other parasite species in the In 2010, 51 male and 50 female cottontails were gathered from an agricultural plain in Italy. Their gastrointestinal tracts were isolated and dissected so that their intestinal contents could be examined with a stereoscope to collect parasitic worms. The researchers found the nematode T. affinis After statistical analysis the sex of the cottontails was concluded to have no effect on the presence of T. affinis but young cottontails were more likely to have the nematode than the adult cottontails were. The researchers give possible reasons for the decrease in parasite diversity from the cottontail’s natural range to its inhabitance in Europe, including that some parasites lacked resources to thrive. The overlapped inhabitance of the cottontail and the native European brown hare (Lepus europaeus) may facilitate the transmission of T. affinis. The discovery of T. affinis in the cottontails in Europe may contribute to the study of the competition between the cottontail and hare but more research of parasites in both animals needs to be conducted.

The extent of the researchers’ analysis consists of the identification of the T. affinis and the calculation of its prevalence amongst different ages and sexes of the cottontails. The researchers only provide potential explanations of why only a few nematode species out of the eighteen known to affect the eastern cottontail are being seen in Italy. Evidence from data is not used to support their suggestions that the eastern cottontails introduced to Europe came from a small portion of the whole cottontail population or that conditions for the parasites’ transmission or population development were not met. The researchers found T. affinis in the cottontails of Europe but fail to provide definite reasons as to why it was found in their sample of cottontails.

Although the article does provide the first report of T. affinis in the invasive cottontails of Europe, it does not provide much analysis of the nematode. However, this article suggests possible causes of the T. affinis population distribution which may lead to future studies about that and the effects the parasite species may have on the competition between the invasive S. floridanus and native L. europaeus.

References

Tizzani, P., Catalano, S., Rossi, L., Duignan, P. J., & Meneguz, P. G. (2014). Invasive species and their parasites: eastern cottontail rabbit Sylvilagus floridanus and Trichostrongylus affinis (Graybill, 1924) from Northwestern Italy. Parasitology Research, 113(4), 1301-1303. doi:10.1007/s00436-014-3768-1

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Review: PE and PS Lipids Synergistically Enhance Membrane Poration by a Peptide with Anticancer Properties

In 2008, an exciting lead for a new cancer chemotherapeutic was discovered in the venom of the Brazilian social wasp, Polybia Paulista. [1] Isolated in a petri dish, the protein Polybia MP1 showed a remarkable degree of specificity in cytotoxicity against leukemia, bladder and prostate cancers. Early publications on the protein showed that its mechanism of action was membrane perturbation; it ripped holes in the membranes of cancer cells. As far as chemotherapeutics go, this is new. Most other known chemotherapeutics target cancer cells by attacking peptides or DNA within the cell leaving the drug vulnerable to getting ejected by Pgp pumps embedded in the cell membrane; the cancer cell’s drug resistance mechanism of choice. MP1 bypasses this process by targeting the cell membrane itself, doing its job just as well outside the cell as it does inside.

The specificity however, is what makes MP1 such a fascinating molecule. It acts against cancer membranes leaving normal cells alone. It became clear in 2012 [2] that the reason for this was because the peptide required a certain set of anionic lipids to be present on the cell membrane surface to allow for it to bind and open significantly large pores. These were the lipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) that were normally found in the inner leaflet of the cell membrane in healthy cells. In some cancer cells however, among the other massive changes in trans-membrane protein architecture, certain overexpressed pumps vital for the cancer cell’s increased metabolism carry PE and PS to the outer leaflet along with their usual transports thus enabling MP1.

The question remained however, how exactly do these two lipids influence MP1’s action? A journal article published recently by a UK/Brazilian research group tests this relationship using model membranes loaded with PE and PS lipids to isolate their interactions. The model membranes were large unilamellar vesicles (LUVs), or large bubbles of lipid formed by the hydrophobic interactions of phospholipids in an aqueous environment. In some cases when necessary to test certain hypotheses, even larger vesicles were used, known as giant unilamellar vesicles (GUVs). The research group formed 4 kinds of GUVs/LUVs containing a combination of PE, PS and a neutral lipid with no significant interactions, PC. These vesicles contained either PC/PE/PS, PC/PE, PC/PS or PC by itself.

This article, published in the Biophysical Journal, is a critical piece of the puzzle that explains how this peptide works and how it might be used to treat human disease. The experimental data gathered was grouped behind 5 individual claims about the mechanics of MP1 on PE and PS in a membrane. While the article has its flaws in particular areas of note, it is well written and its arguments are well supported by the evidence. The 5 claims are summarized below with criticism where necessary on the supporting evidence.

1) PS lipids enhance MP1 binding to the membrane

Figure 1

PS containing lipids showed higher K_p values during CD spectroscopy. This laboratory technique outputs a K_p value, the partitioning coefficient_, which increases when more peptides are bound onto the membrane of a LUV. One critique of this section of the paper is that the data interpretation was made quite difficult for the reader. The data plots showed no particular trends by themselves, as seen in figure 1, and the paper is sparse in explaining the mathematical reasoning from which the K_p values were calculated. While CD spectroscopy data interpretation is admittedly complex, a reader not familiar with the technique would have a hard time reaching the same conclusions as the authors with the graphs alone, so a brief explanation of the concepts and more detail on the math would have been beneficial for understanding.

2) Membranes containing both PE and PS are more susceptible to pore formation

Figure 2

Here, LUVs were incubated in a solution containing three (.37, 3 and 10kDa) different sizes of fluorescent dye, the exchange of which could be measured across the membrane using fluorescence microscopy. The amount of dye leakage across the 4 model membranes was plotted against MP1 concentration, in figure 2, to show that PE/PS/PC lipids showed the greatest leakage for the lowest concentration. It is noteworthy that in graph c and d of figure 2, the PC/PE and PC lines are seen overtaking the PC/PE/PS. This is not a contradiction; it shows that at equivalent concentrations of bound MP1 (PS enhances MP1 binding so these graphs normalize the binding of MP1), PE containing membranes have higher leakage rates, as in larger pores are forming. The interesting bit is that PC overtook PC/PE/PS; the authors claim this must be because PS has a minor inhibitory effect on MP1 pore-forming activity, so that at equal bound MP1 concentrations, having PS in the membrane is a disadvantage. The PS inhibition claim was, however, poorly developed and backed only by one set of data that could have easily been a fluke. Further investigation on this matter is needed before drawing any conclusions. The main conclusion of the argument however is solid and well supported by the evidence.

3) GUVs leakage mechanism is shown to follow the all-or-none model

Figure 3

Vesicle leakage can be described in one of two possible models; either the vesicle leaks gradually through a set of small pores, known as gradual release, or gets lysed completely leaking everything at once, known as the all-or none model. A fluorescence-requenching experiment set to measure immediate dye flow from individual GUVs shows that the model is very strongly aligned with all-or-none, as seen in figure 3. The data shows a strong trend but is contradictory to earlier LUV experiments where the vesicles were unquestionably shown to be gradually leaky. This section of the experiment would have benefitted greatly from trying different concentrations of MP1 to induce leakage, since the chosen concentration may have been so high that it caused the all-or-none leakage event. Furthermore, the data was measured from individual GUVs as opposed to populations of LUVs so the data is weaker for drawing conclusions. The explanation offered by the paper, that the pores must have been large and long-lived enough to make the data seem to be all-or-none, is a wishy-washy explanation that works against the strong trend observed in the data.

4) PE and PS synergize to cause MP1 induced leakage faster then either alone.

In the GUV experiment described in the third argument, time was measured between when the MP1 was added to when the first leakage event of the smallest dye occurred. The data table clearly shows the PE/PS/PC GUV having a significantly smaller time to leakage then the other 3 and the data largely makes sense. This conclusion is well supported by the evidence presented.

5) PE containing membranes have significantly higher permeability and pore size.

The time to leakage data discussed in argument 4 was plotted log-linearly against leakage intensity to generate a value for permeability between the 4 membranes. That data was then fed through the Einstein-Stokes equation relating it to fractional permeable area to show that PE containing lipids had greater permeable area sizes (pore sizes) by fraction than membranes that did not contain PE. The resulting data is quite strong. Further supporting this conclusion, atomic force microscopy images show a size difference in the pores of PE containing lipids. The images were the strongest set of evidence for the argument showing an easily discernable difference in size and frequency of the pores, and leave little room for doubt.

Main Citation

All images/figures and content are from and in reference to:

Leite,Natália Bueno, et al. “PE and PS Lipids Synergistically Enhance Membrane Poration by a Peptide with Anticancer Properties.” Biophysical journal 109.5 : 936-47. Web.

Supporting Citations

[1] Wang, Kai-Rong, Bang-Zhi Zhang, Wei Zhang, Jie-Xi Yan, Jia Li, and Rui Wang. “Antitumor Effects, Cell Selectivity and Structure–activity Relationship of a Novel Antimicrobial Peptide Polybia-MPI.” Peptides29.6 (2008): 963-68. Web.

[2] Cabrera, Marcia Perez Dos Santos, Manoel Arcisio-Miranda, Renata Gorjão, Natália Bueno Leite, Bibiana Monson De Souza, Rui Curi, Joaquim Procopio, João Ruggiero Neto, and Mario Sérgio Palma. “Influence of the Bilayer Composition on the Binding and Membrane Disrupting Effect of Polybia-MP1, an Antimicrobial Mastoparan Peptide with Leukemic T-Lymphocyte Cell Selectivity.” Biochemistry51.24 (2012): 4898-908. Web.