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<element name="FairValueAssumptionsTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" id="plx_FairValueAssumptionsTerm" substitutionGroup="xbrli:item" />
<element name="FairValueAssumptionsRiskFreeInterestRates" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" id="plx_FairValueAssumptionsRiskFreeInterestRates" substitutionGroup="xbrli:item" />
<element name="FairValueAssumptionsExpectedVolatilityRates" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" id="plx_FairValueAssumptionsExpectedVolatilityRates" substitutionGroup="xbrli:item" />
<element name="FairValueAssumptionsExpectedDividendRates" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" id="plx_FairValueAssumptionsExpectedDividendRates" substitutionGroup="xbrli:item" />
<element name="SevenPointFiveZeroPercentageConvertibleNotes2016Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="plx_SevenPointFiveZeroPercentageConvertibleNotes2016Member" substitutionGroup="xbrli:item" />
<element name="FourPointFiveZeroPercentageConvertibleNotes2013Member" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="plx_FourPointFiveZeroPercentageConvertibleNotes2013Member" substitutionGroup="xbrli:item" />
<element name="RepaymentsOfRemainingConvertibleDebtThroughNecessaryFunds" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" nillable="true" id="plx_RepaymentsOfRemainingConvertibleDebtThroughNecessaryFunds" substitutionGroup="xbrli:item" xbrli:balance="credit" />
<element name="PfizerMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" id="plx_PfizerMember" substitutionGroup="xbrli:item" />
</schema>
